- Correspondence to Dr Linda Ng Fat, Department of Epidemiology and Public Health, UCL, 1-19 Torrington Place, London WC1E 6BT, UK;
- Received 27 February 2013
- Revised 9 July 2013
- Accepted 16 August 2013
- Published in print 1 January 2014.
- Published online 5 December 2013.
- Published first 28 October 2013.
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