Caption : This network graph shows all the collaborative relations between keywords. The keywords on this graph have been used at least 7 times with other keywords. Each keyword is represented by a circle, the diameter and size of which are proportional to the number of publications over the period. Coloured clusters represent countries who publish more frequently together. A shorter distance between the keywords and a thicker line connecting the circles indicate a greater proximity of these keywords in the articles published.

Source: publication sources from Pubmed. Analysis tool with Vos Viewer software