- Correspondence to Dr Jennifer Tjia, Division of Epidemiology and Chronic Diseases, University of Massachusetts Medical School, Albert Sherman Building, 368 Plantation Street, AS8-2068, Worcester, MA 01605, USA;
- Received 13 November 2014
- Revision received 1 January 2015
- Accepted 17 February 2015
- Published online 26 March 2015.
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