- Correspondence to Professor Xiaolin Wei, Dalla Lana School of Public Health, University of Toronto, 155 College Street, Ontario, Canada M5T 3M7;
- Received 26 August 2015
- Revised 16 May 2016
- Accepted 31 May 2016
- Published in print 1 December 2016.
- Published online 10 November 2016.
- Published first 20 June 2016.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.