Fig. 4

List of unsolved challenges and proportion of articles reporting on them. We highlighted the challenges found in more than 40 % articles (58 total) in red, and challenges found in 30 to 40 % articles (44 to 58) in green
List of unsolved challenges and proportion of articles reporting on them. We highlighted the challenges found in more than 40 % articles (58 total) in red, and challenges found in 30 to 40 % articles (44 to 58) in green