- Correspondence to Margaret E Kruk, Mailman School of Public Health, Columbia University, 722 W. 168th Street, New York, NY 10032, USA;
- Accepted September 2, 2009
- First published October 12, 2009.
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.