Figure 3.

The analysis of related countries and institutions. (A) Network of countries/territories engaged in the research. (B) Network of institutions engaged in the research. In both networks, the larger the node is, the more contribution the country or institution has made to that field. The link strength between two nodes represents their collaborations and the wider the linking is, the more cooperation is between them. The linking strength between the nations and the US is listed as follows: Australia (109), England (114), Canada (221), Germany (104), Sweden (69), and Japan (47). The linking strength between institutes and Duke University are listed as follows: Harvard University (15), Tilburg University (3), Columbia University (8), the University of Washington (24), the University of California, San Francisco (4), the University of Toronto (9), Pittsburg University (6), and Groningen University (2).