Fig. 6

Country collaboration network (cluster 1: 4 [red], Cluster 2: 4[green], Cluster 3: 3[blue], and Cluster 4: 3[lemon],). Source: VOSviewer compilation form Web of Science database. Note: Maximum number of countries per document and minimum number of documents is set at 25 and 7 respectively. Of the 568 countries represented, 14 were met or exceeded the threshold. The bubble size indicates the biggest collaborating country, while the colour represents the clusters and line thickness is the total strength of the corresponding link