- Correspondence to Dr Amy H Auchincloss, Department of Epidemiology and Biostatistics, School of Public Health, Drexel University, 3215 Market Street, 5th floor, Philadelphia, PA 19104, USA;
- Received June 23, 2016
- Revised September 18, 2016
- Accepted November 7, 2016
- First published November 24, 2016.
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