- Correspondence to Dr Shu-Hong Zhu, Department of Family and Preventive Medicine, University of California, San Diego, 9500 Gilman Drive, MC 0905, La Jolla, CA 92093-0905, USA;
- Received 11 March 2014
- Revised 8 May 2014
- Accepted 12 May 2014
- Published in print 1 July 2014.
- Published online 16 June 2014.
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.