- Correspondence to Dr Yvonne Kelly, Department of Epidemiology and Public Health, 1–19 Torrington Place, University College London, London WC1E 6BT, UK;
- Accepted June 25, 2010
- First published October 5, 2010.
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.