- Correspondence to Dr Wei Du, Institute of Population Research/WHO Collaborating Center on Reproductive Health and Population Science, Peking University, Beijing 100871, China; or Dr Ming Wu, Jiangsu Provincial Centre for Disease Control, Nanjing, 210009, China; email@example.com
- Received August 29, 2012
- Revised April 19, 2013
- Accepted April 29, 2013
- First published June 1, 2013.
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.