## 2 Methodology
### Step 4: Included Research Studies Analysis  
In the final step, the eligible and selected studies were analyzed in more detail. Only these studies were used to answer the research questions. The analysis process is presented in the following sections. _RQ1: What are the leading countries, main authors, time periods and term analyses in maritime education related to autonomous ships based on a bibliometric analysis of scientific publications?_  
In assessing the impact of each country, we considered the total number of authors who contributed to all the papers, where the number of individual authors was weighted by the number of publications in all 81 papers. To explain our methodology, in this analysis, we assigned the contributions of authors from a given country to multiple articles based on the number of publications to which they contributed. In other words, if an author from a given country contributed to multiple articles (denoted as 'x'), their contribution was considered 'x' times. Thus, our approach was not to estimate the number of individual authors. Instead, we weighed the number of individual authors based on the number of articles they published, especially when evaluating their contributions to each country. We have also carried out a historical analysis of the publications to determine the attention that researchers have paid to the different topics of maritime education related to autonomous ships. To this end, we used the results of the analysis presented in the next RQ (RQ2) to classify the studies and used the number of publications per year on each research topic to determine the historical trends. Microsoft Excel was used for this analysis. Since the collection of articles included 81 documents, a bibliometric analysis using the open-source software VOS viewer [15] was considered feasible for the term analysis. For a term analysis, there is the full count method and the binary count method. In the full count method, the number of occurrences of a term in the articles is counted. In the binary count method, a score is assigned for whether or not a term occurs in an article, regardless of the number of occurrences. By default, 29 main keywords to be displayed in the images have been selected. This can be increased manually to include the entire set. Again, it is possible to display the entire network with all keywords or to look at the largest parts ofthe network. The full count method was chosen here to give more weight to the keywords that are mentioned more frequently. Unfortunately, for the main authors and co-authors, we could not use the VOS viewer software, which would show the authors and co-authors in detail, because the software does not support the use of scientific papers from more than one source, and we used three sources, as mentioned above. For the authors and co-authors, we used Microsoft Excel for the analysis. We used the results of the analysis presented in the next RQ (RQ2) to classify the studies and used the number of publications per main author. _RQ2: What common themes or categories are found in maritime education research studies related to autonomous ships, and what scientific methods are used in these studies?_  
This was a more complicated part of our analysis because there is no simple approach to classifying research studies. After summarizing the studies under consideration, the classification was based on some criteria, such as the objective of the publications, the methodology used, the systems studied and considered, and the problems addressed. In this sense, the conceptual analysis presented was of great help since it was used to verify the different categories of studies for the classification, even if this information served more as a tool. In cases where the paper fell into two or more categories, we reassessed the most important contributions and the novelty of the paper before assigning it to a group based on the amount of text and effort devoted to a topic. We tried to find topics closely related to maritime education and autonomous ships.