Fig. 3
![Fig. 3](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs13750-020-00196-7/MediaObjects/13750_2020_196_Fig3_HTML.png)
Years of publication of a the 119 articles retained after critical appraisal and b the 204 articles addressing our primary question (before critical appraisal)
Years of publication of a the 119 articles retained after critical appraisal and b the 204 articles addressing our primary question (before critical appraisal)