Figure 6.

The distribution of all the co-cited authors. VOSviewer is a reliable tool for displaying the intellectual base and frontiers of a certain research field by performing co-citation analysis and burst detection. When two references were cited by the third reference at the same time, these two references constituted a co-citation relationship. The strength of the co-citation relationship between the two cited articles was proportional to the similarity of their research contents and the more times they were cited at the same time, the stronger the co-citation relationship was. There were two major clusters. Cluster 1 (blue) included Shaobo Shi, Tao Guo, Zsuzsanna Varga, and Riccardo M Inciardi; while cluster 2 (red) included Daowei Wang, Fei Zhou, Chaolin Huang, and Wei-Jie Guan. These authors occupied a pivotal position in this field.