- Correspondence to Dr Faming Pan, Department of Epidemiology & Biostatistics, School of Public Health, Anhui Medical University, 81 Meishan Road, Hefei, Anhui, 230032, China;
- Received 28 March 2017
- Revised 24 May 2017
- Accepted 27 May 2017
- Published online 30 June 2017.
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.