Nature 
Volume 557 Issue 7704, 10 May 2018
http://www.nature.com/nature/current_issue.html

Comment | 09 May 2018
When will clinical trials finally reflect diversity?
An analysis of drug studies shows that most participants are white, even though trials are being done in more countries, reveal Todd C. Knepper and Howard L. McLeod.
Todd C. Knepper  & Howard L. McLeod