## 2 Bibliometric Analysis Research Methodology
### Bibliometric Analysis Methodological Process: A Five-Step Approach  
Bibliometric analysis is a widely recognized method in library and information science that employs statistical techniques to systematically evaluate scholarly literature, integrating both quantitative and qualitative dimensions [21]. By examining citation networks, this approach pinpoints central authors, influential publications, leading journals, and foremost research institutions. Moreover, it uncovers thematic clusters, dominant research trends, and emerging topics across academic disciplines, thereby providing researchers with an impartial framework for identifying foundational works and tracking significant developments within their fields [22]. Authors [23] have highlighted the distinct strengths of bibliometric analysis, notably its ability to quantitatively chart scholarly research areas. This approach systematically organizes extensive bodies of academic literature, facilitating the creation and appraisal of evolving knowledge structures. The scholars recommend supplementing methods with qualitative techniques, such as content analysis, to interpret unstructured data, including texts, images, and symbols. This ensures methodological rigor, reproducibility, and transparency regarding bibliometric studies yielding reliable and unbiased results. As a result, these methodologies substantially improve literature reviews by offering systematic and replicable evaluations that produce robust and trustworthy insights [24]. This lays the foundations for developing a five-step approach for implementing the bibliometric analysis research methodology regarding the green shipping corridors research domain, as presented in Figure 1.  
The diagram depicts the five-step bibliometric analysis approach utilized to map and analyze the green shipping corridors research domain. The five steps are briefly discussed as follows:  
Figure 1: Five-step bibliometric analysis approach. * Step 1. Data Collection through ISI Web of Science Search: A comprehensive search was conducted in the ISI Web of Science (WoS) database, incorporating relevant keywords, Boolean operators, and search filters. A total of 238 articles were identified, forming the final dataset, as presented in Table 1.  
* Step 2. Bibliometric Analysis and Network Construction: Two bibliometric software packages were employed, VOSviewer and the bibliometric package in R. The selected 238 articles were analyzed in VOSviewer to construct a network of interconnected document clusters, as stated in Appendix A. VOSviewer is a specialized software developed for the construction and visualization of bibliometric maps [25]. VOSviewer is easy to operate, offering numerous visualization options--co-citation, bibliographic coupling, co-word, and co-author network analyses--and supports combining data from multiple databases (ISI WoS and Scopus). In contrast, other bibliometric software options, such as CiteSpace's data preparation, can be confusing, and its clustering may fail in emerging fields, while Gephi (version 0.10) requires pre-processing data using Bibexcel or Excel [26]. The bibliographic coupling methodology applied to 15 citation links per document resulted in a total of 115 articles in the network. The bibliometrix package in R revealed the foundational insights regarding the green shipping corridors research domain, located in Section three of the article. * Step 3. Thematic Clustering: The employment of bibliographic coupling revealed a threshold of 15 shared references per article. This approach enabled the distinguishing of four thematic clusters, each with its own subclusters, collectively encompassing 115 articles from the original dataset. * Step 4. Selection of the Most Influential Articles in the Clusters: Articles within each of the four clusters were assessed according to two key VOSviewer metrics, (1) Total Link Strength, reflecting the extent of an article's connectivity within