- Correspondence to Abigail J Enoch, Nuffield Department of Population Health, Richard Doll Building, Old Road Campus, Headington, Oxford OX3 7LF, UK;
- Received August 25, 2015
- Revised October 21, 2015
- Accepted October 24, 2015
- First published December 23, 2015.
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
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.