- Correspondence to Dr A D Simms, Centre for Epidemiology and Biostatistics, Level 8, Worsley Building, University of Leeds, Clarendon Way, West Yorkshire, Leeds LS2 9JT, UK;
- Received July 26, 2012
- Revised August 16, 2012
- Accepted August 17, 2012
- First published September 22, 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.