- Correspondence to Dr Andrew T Chan, Clinical and Translational Epidemiology Unit, Massachusetts General Hospital, 55 Fruit Street, GRJ-825C, Boston MA 02114, USA;
- Received 4 April 2016
- Revised 31 May 2016
- Accepted 12 June 2016
- Published in print 1 July 2016.
- Published online 19 July 2016.
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