Research in International Transfer of Vocational Education and Training – A Systematic Literature Review

Context : The transfer of vocational education and training (VET) has a long tradition and can be based on various conceptual and methodical approaches. Transfer process and success can be influenced by numerous factors at different levels (systemic, institutional and individual). However, the existing research on the challenges and success factors of VET transfer is very heterogenous and fragmented. Method: To provide a comprehensive and structured overview of the current state of the international research on transfer in the context of VET, we conducted a literature review, which is presented here. Using the method of systematic literature review, a total of 231 studies were found and 41 studies were selected based on the defined criteria for full text analysis. Findings: Various specific research foci and analytical approaches used on the included studies were identified and documented. The transfer of a dual VET system or its elements is based on different approaches and perspectives of the recipient country and the transferee. Major challenges for the transfer of dual VET systems include the social reputation of VET in the recipient countries and (language- and culture-related) communication difficulties between the involved parties. For a successful transfer of VET, a deeper knowledge of the contextual conditions in the recipient country are of particular importance, as well as a close, longstanding cooperation between the involved parties. Conclusion: The generated knowledge about key contextual conditions at the individual, company and systemic level in the context of VET transfer can provide a valuable basis for future VET cooperation.


Theoretical Background to Research in International 'VET Transfer'
The process of internationalization is becoming increasingly important in the area of vocational education and training (VET) (Frommberger & Baumann, 2019). In particular, international cooperation in VET has been regarded as an essential way of shaping internationalization for decades, as the practice of transferring educational structures internationally has a long tradition (Barabasch & Wolf, 2011;Frommberger & Baumann, 2019). In this context, the transferability or exportability of VET systems or its elements to other countries has been investigated for many years, for instance (Barabasch & Wolf, 2011;Clement, 2012;. Research and scientific studies in this area have increased in recent years (Dobischat & Düsseldorff, 2018), while numerous international cooperation projects have been ongoing for years, for example in the United States or India (Gessler, 2017;Pilz, 2016). In the literature, very different understandings, conceptualizations, and models of 'transfer' in VET research can be found. At the same time, rather limited knowledge about the heterogeneous models and approaches leads to a fragmentation of the research landscape . To bridge this gap, it is necessary to structure, systematize, compare and, if necessary, integrate different disciplinary research approaches.
In regard to the significance of the topic in terms of research, practice and policy, the primary goal of this article is to prepare a comprehensive, structured overview of the current state of international literature on transfer in the context of VET research. The authors systematically analyze the current international state of research on transfer with a multidisciplinary and multi-level perspective by using the method of "systematic literature review" (Gessler & Siemer, 2020;Grant & Booth, 2009). The identification of thematic and methodological foci and of semantic and/or structural links between the various approaches, theories and best practice models is a central focus of this article. Furthermore, indications of international networking and synergy potential in this field of research are taken into account.

Concept of (Professional) Competence and Understanding of VET Transfer
To provide a comprehensive and structured overview of the current state of international research and to analyze the multidisciplinary perspectives on transfer in the context of VET, 140 Transfer in VET -A Systematic Literature Review in a first step, it is necessary to define the understanding of the two core concepts in VET research, namely "transfer" and "(professional) competence".
With the globalization of the labor market, an increase in the importance of harmonized educational, and especially VET, systems became evident. This refers to the international innovation and competitiveness of organizations involved in VET as well as to the importance of ensuring competences for (international) professional mobility and self-reliant living of citizens and enabling lifelong learning, which is necessary in an increasingly changing societal and technological environment (e.g., Baethge et al., 2006;DIHK, 2015).
The harmonization trends in VET call for an internationally comparable (high) level of qualification in the respective national VET systems (e.g., Cedefop, 2011;Dunkel & Le Mouillour, 2013). In the last decade, the European Union has intensified its efforts to create more transparency within the VET systems in Europe and to regulate the harmonization of vocational qualifications with the development of the European Qualifications Framework (EQF) and the European Credit Transfer System (ECVET). Furthermore, as part of an international comparative feasibility study on VET (the so-termed 'VET PISA'), a largescale assessment framework was developed in response to the increased importance of the VET systems to assess their learning outcomes, i.e. professional competencies. This feasibility study impressively showed that competences targeted in VET have to tow the line between meeting the requirements for both national particularities and international comparability (Baethge et al., 2006). This tension also applies to the sense of the transferability of nationally established VET concepts to other countries. Since in-company instruction and training programs tend to be heterogeneous and less formalized, teaching-learning and examination approaches, adaptation and transfer in VET systems are accompanied by a variety of challenges (e.g., Kuper & Schrader, 2013).
The concept of transfer is defined differently in various disciplines and contexts (Gräsel, 2010). Educational transfer is based on the conceptual nuance of transference and is defined by Gessler (2012) as the transfer of educational ideas, structures, and practices from one system or institution to another. The term transfer in an educational context is primarily a term used in German-speaking countries, although export is also frequently used as a synonym (Geiben, 2017). In the international context, the general term policy transfer is primarily used to describe this concept . While policy transfer encompasses educational transfer, it is often described in a broader sense as the transfer of concepts or procedures. In addition, policy transfer can be further differentiated to refer to policy learning, policy borrowing, policy diffusion, policy reception and policy lending, depending on the academic discipline and the scope of the transfer (Dolowitz & Marsh, 1996;Geiben, 2017;. Referring to the definitional approaches, Geiben (2017, p. 23) defines transfer in the context of VET cooperation as "the transfer of ideas, practices and products as well as assumptions from one or more countries to one or more different countries." This article, which aims to comprehensively review existing research literature on this topic, is guided by this broad definition.
The VET system, for instance in German-speaking countries, represents a historically evolved complex constellation of participating institutions and actors that cannot easily be exported Strittmatter & Böhner, 2019). In the context of international VET research, many studies therefore concluded that the transfer of a VET system cannot take place as a one-to-one transfer (Stockmann, 2013;Stockmann & Silvestrini, 2013). In this regard, the transfer process cannot be seen as a copying process but needs to be designed as a selection and adaptation process that supports partner countries in adapting elements of their existing systems (Euler, 2013).
In this context, another important core concept in VET research, also at the international level, refers to the concept of competence. The term competence has become a fashionable term in the social and educational sciences (Klieme & Hartig, 2007). A broad use of this term can also be found in educational policy and research. However, the term competence, has different meanings in literature and everyday understanding, and it is neither used nor applied consistently in research and practice. Even in research dealing with educational and learning processes, competence is not defined synonymously, and is conceptualized and operationalized differently (Hartig, 2008;e.g., contributions in Blömeke et al., 2013).
The definition of the construct competence is a fundamental prerequisite for empirically sound investigations of learning and educational processes. However, it is precisely in the definition of competence as well as in the development of well-founded theoretical competence models that the challenges of empirical competence research become evident (e.g., Blömeke et al., 2015). These difficulties are partly due to the different and partly incompatible roots of the concept of competence across disciplines (Klieme & Hartig, 2007). This is particularly true for VET that is characterized by a high heterogeneity of domains as well as participating institutions and actors. Moreover, the VET research is based on different (in parts nation-specific) traditions and conceptual and theoretical approaches, leading to a variety of (domain-specific) definitions of competence, including (i) competence in a purely organizational sense with regard to responsibility in an institution, (ii) psychological understanding of competence as disposition (e.g., professional knowledge), (iii) general understanding of competence as expertise, (iv) specific vocational skills or a holistic concept of (professional) performance (e.g., Shavelson, 2013).
In German-speaking countries, competence is often understood as the comprehensive ability to act and to master a specific (e.g., professional) situation, which can be subdivided, for instance, into domain-specific, personal, and social competence. This triad is specifically 142 Transfer in VET -A Systematic Literature Review taken up and further developed in German VET with the concept of 'vocational action competence' (Jude & Klieme, 2008;BiBB, 2010). In this context, action-and problem-oriented learning, the orientation toward professional competence in the sense of a broad holistic understanding of competence, as well as the training of trainers, and the development of cooperation between institutions involved in VET are established as core elements in the German dual training system (Angles & Lindemann, 2019).
In the current research, the German funding program ASCOT (Technology-based Assessment of Skills and Competences in VET) systematically analyzed, among others, competence characteristics of trainees at the end of their training. Based on technology-based assessment instruments for competence diagnostics (mostly computer-based simulations), evidence on the performance of trainees at the end of their VET is available for various occupations. The findings from the assessments indicate that the required higher-order skills such as problem-solving and reflective competencies are not consistently achieved in VET (see contributions in Beck et al., 2016;Seeber & Seifried, 2019). Not only on a national level but also on an international level, there is a great variety in usage of the term competence, of definitions of competence, and its modeling. The diverse conceptualization of this term on an international level is also reflected in the various classification systems and systematizations of definitional approaches (e.g., Le Deist & Winterton, 2005;Mulder et al., 2007). In this context, classification systems for countries and regions show different approaches to defining competence with regard to VET, such as behavioral competencies including functional and cognitive competencies (USA), an occupational (functional) competence model including cognitive and behavioral competencies (UK), and more holistic approaches (France, Germany, and Austria) (Le Deist & Winterton, 2005).
To summarize, the concept of competence in international VET research is a prominent yet relatively new paradigm that is anchored in the respective socio-cultural context and, thus, shaped by national or even regional context-and domain-specificity. This makes the transfer of VET systems even more challenging.

Systematic Literature Review
The aim of a systematic literature review is to provide an overview of the current state of research on a particular topic and to draw theoretical and/or practical implications from it (Kitchenham & Charters, 2007;Xiao & Watson, 2017). In this context, Oakley (2017, p. xiii) highlights the benefits of a literature review compared to a single study: "The aim of syste-matic research synthesis is to generate a more comprehensive and trustworthy picture of the topic being studied than is possible from individual studies". This article presents a systematic analysis of the current international state of research on VET transfer with a multidisciplinary and multi-level perspective by following Gessler and Siemer (2020). According to their categorial definition, a systematic literature review covers the four following steps: (1) Definition of the scope, (2) data selection, (3) data processing, and (4) data reporting (Gessler & Siemer, 2020). The following part presents the literature review and its results according to these four categories.

Scope Definition
The scope definition specifies the research problem and derives central research questions. Within this literature review, the authors systematically analyze theoretical-conceptual as well as empirically oriented research on VET transfer with a multidisciplinary and multilevel perspective (Euler, 2019;Phillips & Ochs, 2003;Rappleye, 2006;Tanaka, 2005). The identification of thematic and methodological foci as well as semantic and/or structural links between the various approaches, theories and best practice models are a central focus of this article. Furthermore, indications of international networking and synergy potentials in the research field are taken into account. The central research aim of this literature review is to analyze the international state of research and to structure the knowledge base for the description of the object of investigation, "transfer research in VET," as well as a downstream analysis of its contextual conditions and determinants (i.e., major challenges and key success factors of transfer in international VET research).

Data Selection
The next step, data selection, entails a systematic search and eligibility screening. The sources and search terms have to be defined and the relevant research has to be selected, screened and read, whereas the ineligible research should be excluded. The determination of relevant sources to be included was done through a multi-step approach. To ensure a systematic and replicable approach to the analysis of the international state of research, central relevant literature databases such as Education Resources Information Centre (ERIC) and Google Scholar were used. In addition to the systematic literature search, the "snowball technique" was applied to collect additional references from identified papers (Waddington et al., 2012): After reviewing the first set of relevant literature, keywords and keyword combinations were determined to find further relevant publications. Thus, the approach of the review presented here is based on an extensive search from central education-research-specific online databases: Fachinfor- Based on the research question, keywords were extracted to specify the search and to thus make it easier to identify relevant publications. Different authors (Bayliss & Beyer, 2015;Xiao & Watson, 2017) emphasize the importance of keywords in the search for relevant literature. In addition to the degree of precision of keywords, the use of the Boolean operators "AND" and "OR" is also crucial for a targeted search . In our search, the keywords listed below were combined by means of these logical links. Furthermore, the use of different terms within the national and international research landscape was taken into account, as the term transfer has different variations (see Table 1).
The identification of relevant studies was also complemented by drawing on project publications and reports as well as the "snowball system" to find additional literature to complement the formally published research (Adams et al., 2017). Especially in the context of vocational education, Haßler et al. (2019, p. 34) emphasize the importance of including different publication outlets, as "numerous important activities are not covered in professional journals." To find publications of this kind as well as other relevant studies, Google Scholar was used. In addition, using the snowball system meant that references in previously identified papers were sifted through, further contributing to the completeness of the documentation of the current state of research (Waddington et al., 2012;Xiao & Watson, 2017). Related terms and synonyms in the context of VET transfer were therefore also searched for. This approach led to the definition of a number of German and English keywords (see Table 1). This procedure also resulted in a large number of search results, as irrelevant literature could not be avoided in the hit list. Furthermore, due to searching several databases and using similar search strings, duplicates were also elicited, which were excluded in a first step (Sturma et al., 2016;Tonhäuser & Büker, 2016).

Data Processing
The third step, data processing, focuses on critically assessing the quality of the selected literature to exclude unsuitable search results and to select the relevant data from the consulted resources, and then critically evaluate the (preliminary) selection of sources. This step also involves synthesizing and re-analyzing the selected data. Accordingly, the next step of our literature review was to analyze the titles and abstracts of the publications identified by the database search with regard to their relevance. Obviously thematically irrelevant papers could then be excluded, while publications that were significant for answering our research question were examined more closely in their entirety. In addition, the relevant publications that were identified using the "snowball system" and the search for "gray literature" were also read in full.
Finally, the remaining articles were selected based on predefined inclusion criteria ( Kitchenham & Charters, 2007;Sturma et al., 2016). To be included in the next step of the systematic review, studies had to meet the inclusion criteria listed below (see Table 2). Consequently, the criteria also served as exclusion criteria, i.e., if a study did not meet these criteria, it was excluded.

Table 2: Criteria for the In-and Exclusion of Studies
-The study is written in German or English.
-The study was published between 2010 and 2020.
-The thematic focus of the study is on transfer of VET systems and/or elements.
-The study has been published in a peer-reviewed journal or book 146

Transfer in VET -A Systematic Literature Review
The final selection and systematization of the studies is based on a criterion-guided classification into several higher-level categories such as study focus, research method, sample, participating countries (for an overview, see Table 4 in appendix).
In the course of the systematic literature search, the selected search terms (see Table 1) were entered and combined both as keywords and as free text, as this approach proved to be particularly effective. In this way, a total of 331 studies were identified. Of these, 325 studies had been found through the database search, while the remaining studies resulted from the "snowball system" and the search engine Google Scholar. Since the databases are constantly updated, this can lead to a different number of hits for the search query at later dates.
Doublets were checked using the reference management program Citavi, and we subsequently conducted a duplicate comparison. This eliminated 100 doublets of potentially relevant and irrelevant studies, which resulted in a remaining number of 231 studies for the title-abstract screening, in which the relevance of the studies was assessed based on their titles and abstracts. After this screening, 140 publications were excluded from the review as it was evident from the title and/or abstract that they did not address the topic of VET transfer in a narrow sense. Among the remaining publications were studies that, for example, dealt with the transfer of knowledge from theory to professional practice (Frey et al., 2014) or focused on the international mobility of apprentices in the context of internationalization (Friedrich et al., 2010).
As a result, 91 studies remained that were deemed relevant. The full-text versions of these studies were obtained and read. Based on the predefined inclusion criteria (see Table 2), 41 relevant studies were identified that proved to be thematically and methodologically relevant and were therefore included in the present literature review. Thus, 50 publications were excluded which could not yet be rejected during the title-abstract screening, but which turned out to be less relevant in the full-text review. In addition, the analyses of the full texts revealed that relevant information ensuring the research quality of the studies, i.e., basic information on the method, sample size, and analysis approach, was often missing or not described sufficiently. Hence, about one dozen of the studies that initially appeared relevant could not be included in the review due to fundamental information missing and/or obscured.

Data Reporting
The final step of our systematic literature review focuses on data reporting, and it involves presenting the findings and implications as well as the limitations of the review and discussing the conclusions.
In the following section, an exemplary selection of the included studies is presented, taking into account theoretical or conceptual and application-oriented studies. The key findings and implications are presented and discussed as well. The final part of the step data reporting, namely presenting the limitations, is presented in Section 4.

The Current State of Research in VET Transfer
The The central research aim of our literature review is to analyze the international state of research and to structure the knowledge base for the description of the object of investigation "transfer research in VET", as well as to conduct a downstream analysis of its contextual conditions and determinants (i.e., challenges and success factors of transfer in international VET research). In the following part, the central key findings will be summarized and their implications for our research question will be discussed. 148 Transfer in VET -A Systematic Literature Review

Key Findings
In the following, we present an exemplary selection of the included studies consisting of theoretical or conceptual and application-oriented studies. The 40 studies included in this research literature review (see Table 4 in appendix) address the topic at different levels. The majority of studies included (approximately three-quarters) deal with transfer processes on a systemic level and approximately one third examine transfer from a corporate or entrepreneurial perspective and/or at a VET institutional level; approximately one-sixth of the selected studies considered both levels. As defined in Section 2, all studies, regardless of their specific focus in the area of transfer research in VET, were initially included in the mapping procedure. To structure and systemize the studies and their findings, we summarize them and present key challenges and key success factors of VET transfer as stated in the research papers. Thereafter, the studies were categorized and classified according to their methodological approach, identifying six studies that addressed the topic of transfer on a theoreticalconceptual level, 30 studies that dealt with the topic empirically, and four meta-studies that examined transfer processes based on literature reviews or a meta-analysis (see Table 4 in appendix).
In the literature review, we identify several studies dedicated to the implementation of a dual VET system with different approaches. In addition to ideas for a possible business model to promote and commercialize dual vocational education (Jonda, 2012), other studies focus on VET policy transfer (Barabasch & Wolf, 2011), on piloting a scientific transfer model in practice (Bohlinger & Wolf, 2016), or they identify training strategies used by German companies abroad (Körbel et al., 2017).
Another central focus in various studies is the transfer recipient country and the perspective of the transferee (Barabasch & Wolf, 2010;Bohlinger & Wolf, 2016;Euler, 2019). Here, a common finding is that the understanding of duality needs to be clarified and core challenges need to be addressed as part of the design of the transfer process. The insight that the transfer cannot take place as a one-to-one copy is the result of many studies (Euler, 2013;Hummelsheim & Baur, 2014;Stockmann, 2013). Instead, VET transfer is about adapting to the context of the recipient country and introducing appropriate, for instance, dual training elements (Euler, 2013;Ramasamy, 2020).
The analysis of the research literature shows that there is not just one way of implementing specific, for example competence-oriented, training structures. Rather, there is a variety of different approaches to establishing VET elements (that are based on, e.g., the German model). Different VET elements can be introduced at different levels. The examined implementation approaches range from the development of a business model idea at the system level (Jonda, 2012) to the establishment of an autonomous qualification center at the individual company level (Krzywdzinski & Jürgens, 2019). Therefore, the analysis of the transfer conditions plays a major role in transfer approaches. These strategies include a systematic further development of vocational education at the micro, meso and macro levels. According to the analyzed studies, the development of legal frameworks could be identified as an implementation measure on the macro level (Barabasch & Wolf, 2010Krzywdzinski & Jürgens, 2019); on the meso and micro level, measures included the modification of certifications and curricula and the creation of further training measures for students and teachers (Bohlinger & Wolf, 2016;Krzywdzinski & Jürgens, 2019). The choice of the respective strategy is conditioned by internal as well as external influence factors, i.e., that the implementation or transfer approaches can vary considerably from country to country or even from company to company (Körbel et al., 2017).

Key Challenges in VET Transfer
One of the key challenges in the transfer of VET elements is the low social standing of the VET system in many countries. In this context, the included studies observed that the acceptance of VET institutions as an equitable alternative to academic education is low in many target countries (Fraunhofer MOEZ, 2012; Van der Burgt et al., 2014;Welfens, 2016). As a consequence, companies are less willing to invest in complex VET elements, which results in generally low investments in the VET system in the respective countries (Wiemann, 2020;Wiemann & Pilz, 2020).
Furthermore, a central challenge in VET transfer is rooted in communication difficulties (Fraunhofer MOEZ, 2012;Haering et al., 2014;Pfaffe, 2019). These communication barriers can be attributed to both linguistic and cultural differences (Li, 2017). For example, in many target countries there is a lack of English language skills on the part of trainees, trainers and project officers, which can have an aggravating effect on transfer activities (Haering et al., 2014). Since the transfer process requires a great deal of coordination between the involved parties, successful communication is essential (Peters, 2019a). Here, the support of technical, linguistic, and cultural experts in both the recipient and transferring countries is needed (Li, 2017).
In addition, some studies indicate that transfer activities can be met with distrust and resistance from different stakeholders (Bohlinger & Wolf, 2016;Krzywdzinski & Jürgens, 2019;Pfaffe 2019). This skepticism can be attributed to different causes: In addition to different traditions in the recipient countries to which the participants want to adhere, negative previous experiences with transfer activities can also lead to resistance (Bohlinger & Wolf, 2016;Krzywdzinski & Jürgens, 2019;Eichhorst et al., 2012). 150 Transfer in VET -A Systematic Literature Review

Key Success Factors in VET Transfer
Beside the challenges listed above, the literature reviewed also reveals success factors for the transfer of VET elements to other contexts. According to numerous reviewed studies, knowledge of the contextual conditions and the resulting adaptation to the conditions in the target country is a prerequisite for the successful implementation of VET elements (Bliem et al., 2014;Fraunhofer MOEZ, 2012;Peters, 2019aPeters, , 2019bPfaffe, 2019). This is consistent with the notion that transfer must be a process of adaptation and adjustment. In this context, the example of Stockmann (2019) points to the importance of flexible project management that reacts to changing environmental conditions and does not stick too rigidly to the original model.
Furthermore, close cooperation between the involved parties is stated as an important basis for successful VET transfer (Aring, 2014;Gessler, 2019). Therefore, constant communication is necessary to prevent misunderstandings and conflicts of interest. Furthermore, a reliable basis of trust between the participants can be established through constant exchange (Peters, 2019b). This relationship-building is not limited to bilateral cooperation between national and international partners. All stakeholders involved should also cooperate closely with each other and show a similar understanding of as well as trust in the targeted transfer project.
In addition, the role of individuals and the competence of instructors as well as other decision-makers is an important influencing factor (Dowling et al., 2008). In particular, knowledge of how the relevant VET system works has a significant impact on the success of the transfer process (Wiemann & Pilz, 2020). Here, the participation of trained and experienced expatriates or trainers, especially at the beginning of the transfer activities, constitutes a positive influencing factor for a successful transfer (Körbel et al., 2017).
Another success factor consists of having a goal-oriented organization with transparent structures. In this context, it is important to clarify responsibilities and the associated accountability at both state and private-sector level (Bliem et al., 2014;Peters, 2019b;Stockmann, 2019). Considering the large number of actors involved in VET transfer, it is of great importance that the organizational structures and the distribution of tasks are presented transparently to create binding framework conditions for the dual system (Krekel & Walden, 2016).
A number of studies also draw attention to the importance of companies' willingness to provide training (Bliem et al., 2014;Gonon, 2014;Krekel & Walden, 2016). Only if companies are willing to invest in training activities can the potential of VET structures be tapped. To ensure the commitment of involved companies, the training costs incurred must be outweighed by corresponding training benefits for the companies (Bliem et al., 2014;Krekel & Walden, 2016;Langthaler, 2017).

Implications
The systematic literature review of international VET research indicates that ex-ante evaluations of key concepts and approaches underlying one particular VET system and its central contextual (e.g., socio-cultural) factors should be conducted before beginning a transfer process to assess the transfer project's chances of realization and at the same time to be able to provide effective training in accordance with the local labor market (demands) (e.g., Stockmann & Silvestrini, 2013). The primary objective of this evaluation is to provide a broad prospective analysis of both the situation in the transferee and recipient country before the transfer activities begin, so that possible barriers can be identified before they occur (Wiemann, 2020). In this context, an analysis of the various local institutions and actors involved should take place (e.g., Pilz, 2017). Gessler (2017) suggest that by analyzing the financial situation of potential trainees in advance, effective measures could be developed to create an incentive to take up and complete training. Furthermore, the respective national framework conditions must be examined, as these in turn impact the demand for specific training structures and targeted outcomes (Pilz, 2017). In addition, legal regulations and institutional responsibilities in the transferee countries must be evaluated in terms of whether they are compatible with the system in a recipient country.
The adaptation of VET approaches to the actual conditions in the target countries is closely linked to the aforementioned ex-ante evaluation of the contextual conditions. Adaptation processes require, in particular, flexibility in transfer that responds to the changing influencing factors (e.g., Stockmann, 2019;Wiemann & Pilz, 2020). It is essential that the reference model is not followed too rigidly and that appropriate adaptations are developed within a local cooperation (Wiemann & Pilz, 2020). As part of the adaptation processes, for instance the infrastructural requirements or the economic structures of the target country must be taken into account to adapt the transfer approach accordingly.
The results of the present analysis of the state of international VET research clearly show that individual persons involved in the transfer process, can have a great influence on VET transfer. The findings indicate that the professional expertise of the actors involved should be examined and, if competences are lacking, measures should be established to effectively address these deficits. In particular, the training of teaching staff is of great importance in the context of VET transfer. The quality of trainers can be consequently improved through higher-level training or education opportunities based on international standards (e.g., Gessler, 2019; Körbel et al., 2017;Peters, 2019b).
Another important aspect to ensure successful international cooperation and VET transfer is the communication between participants involved. Particularly with regard to the sustainability of the transfer process, continuous communication and cooperation between VET practitioners from various institutions is required. In this context, the socio-cultural impact of communication is often underestimated, giving way to misunderstandings (e.g., Lange & 152 Transfer in VET -A Systematic Literature Review Hohnwald, 2008). As a result, in the course of VET transfer, the communication culture of the countries and institutions involved should be examined and considered in the adaption to the recipient country (Li, 2017). For instance, when translating into local languages, it should be ensured that the translators are familiar with the cultures involved and can thus assure a translation that is appropriate to the meaning, i.e., functional equivalence (Li, 2017).
The research analysis suggests that communication is a central influencing factor in VET cooperation and transfer on several levels. For example, transparent organization of responsibilities should ensure communication between various stakeholders, including the state, private businesses, trade unions, educational institutions, educational staff, and trainees. Therefore, instruments that enable or promote the exchange between the participants involved are required, and relatively flat hierarchies and constant communication should be paid attention to (Kenzhegaliyeva, 2018). In the future, digital solutions to support supra-regional communication and cooperation in VET should be further developed and systematically implemented.

Limitations and Outlook
This section outlines limitations of the presented literature review in terms of theoretical and methodological issues as well as regarding the systematic processing and analysis of the studies. Finally, an outlook on further research needs is provided. Although the review was guided by established methodological and research standards to ensure a methodologically sound approach, it cannot be ruled out that some relevant studies were not found and included (Sturma et al., 2016). Although the systematic search approach using several keyword combinations in different databases reduced the likelihood that relevant studies were disregarded, there is still a risk that relevant publications were not included in the present literature review . In general, using the inclusion criteria applied may be accompanied by the exclusion of potentially relevant studies. This might be due to the fact that only publications in German and English were included in the review, thus possibly leading to an exclusion of relevant literature in other languages. In addition, only studies published in a specific time period (2010-2020) were considered. These decisions were necessary due to time and cost constraints and for efficiency reasons, as a translation of studies published other languages would have exceeded the available scope. However, since the transfer of VET is controversially discussed internationally and hence there may be literature available in languages other than German or English, it would be interesting to consider these studies in future work.
As a further general limitation, Sturma et al. (2016) emphasize that the involvement of several people in the search, selection and evaluation process can significantly increase the objectivity and thus the quality of the literature review. Thus, the objectivity of the sub-pro-cesses of the present review must be considered critically, as both the choice of databases and the formulation of the inclusion criteria are based on the national perspective of the authors. The same applies to the definition of the keywords and the literature search itself. The objectivity of the present work could have been increased by involving external experts from the same research discipline in the process, especially when creating the search terms (Klatt, 2019).
There might also be limitations regarding the processing and analysis of the included studies. As the literature review using a narrative approach by Li and Pilz (2021) has shown, VET transfer research is based on various academic disciplines. Overall, Li and Pilz (2021) provide a broad understanding of VET transfer and underline the high complexity and challenges of VET transfer. In the review presented here, we used a similar broad approach to transfer in VET in our analysis. The studies included here can certainly be analyzed in greater depth. One common finding regarding the methodology of the assessed literature is that the majority of the included publications is based on a case-study approach Krzywdzinski & Jürgens, 2019;Peters, 2019a). This method is not without controversy, and its representativeness and generalizability are often challenged (Hildenbrand, 1991;Simons, 2009). In addition, there is criticism that case studies often show a certain inaccuracy and lack of objectivity (Rowley, 2002;Yin, 2009). However, case studies allow for "deep insights into the object of investigation" (Peters, 2019b, p. 83) and accurate and in-depth research in socio-political contexts (Kelle & Kluge, 2010).
Overall, the studies examined differ in their methodology and in their sample composition, in some cases considerably. The broad mapping approach was chosen to obtain a comprehensive overview of the current state of research. However, this affects the comparability of the results. Even though the present study attempted to systematically arrange the studies according to the level at which they address transfer, it cannot be assumed that their respective results are directly comparable with each other. For future reviews, it would be conceivable to include only those studies that are based on the same methodology and/or focus on the same source and recipient countries.
Furthermore, our analyses demonstrate a general limitation: a significant number of the studies screened during the literature review did not provide sufficient fundamental information that would be expected by any research publication, i.e., precise descriptions of research methods, procedures used, sample descriptions, materials, and evaluation approaches (see also Section 2.4). This limitation indicates that higher compliance with research quality standards need to be ensured for the future publication of research results in this area. This is also a necessary prerequisite to ensure stronger connectivity of studies to the current state of research as well as replicability of the findings. A greater emphasis should be placed on the call for these requirements in the future research in this field. 154

Transfer in VET -A Systematic Literature Review
One focus of this review was the German dual VET system as a transfer object. In future research, it would be useful to compare the implementation approaches and success conditions for the transfer of the German VET system to those for the transfer of comparable dual vocational training systems. In this way, fruitful findings regarding the respective vocational training transfers could be made compatible for practitioners in the field of VET cooperation.
In general, the majority of the included studies is based on an investigation of a recipient country or company. Future research activities should therefore focus more on a comparative approach that compares and analyzes the transfer of dual vocational training in different countries and/or companies.
Despite these limitations, the present work succeeded in combining and analyzing research publications on the transfer of VET systems with regard to implementation approaches and the framework of conditions at different levels of observation. Thus, a comprehensive overview of implementation approaches and conditions for success was provided, which offers important insights for VET practitioners. The generated knowledge about important contextual conditions on an individual, company and systemic level in the context of vocational training transfer can offer numerous starting points for future vocational training cooperation or vocational training export to make transfer even more target-oriented. There is no single solution -but versatile approaches and strategies can serve as orientation aids to enable the successful transfer of vocational training systems across borders in the future. 1 Identifying key processes related to the transfer of core elements of the German dual training system to the SENA-TI training program Presenting lessons learned from the experiences, results and successes of the work performed by the "Regional Association for Technical and Vocational Education" (RAVTE) in the ASEAN region; perspectives for the use and development of regional structures for VET research, systems, and cooperation Interviews with managers and engineers of the construction company; expertinterviews with construction engineers from German companies; discussions with local engineers and managers to understand the structure and regulations of Egyptian construction work Germany, Egypt Wolf (2013); see also Wolf (2017) (2019)