- Correspondence to Dr Kelvin Choi, Division of Epidemiology and Community Health, University of Minnesota, 1300 South Second Street Suite 300, Minneapolis, MN 55454, USA;
- Received December 12, 2011
- Accepted June 28, 2012
- First published July 20, 2012.
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.