- Correspondence to Dr Diana Maria Sanchez, UNC Gillings School of Global Public Health Department of Epidemiology, Chapel Hill, 2104D McGavran-Greenberg, CB #7435, Chapel Hill, NC 27599-7435, USA;
- Received March 29, 2015
- Revised September 17, 2015
- Accepted October 17, 2015
- First published November 16, 2015.
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