- Correspondence to Janet E Rosenbaum, Department of Epidemiology and Biostatistics, School of Public Health, SUNY Downstate Medical Center, Brooklyn, 450 Clarkson Ave, Mailstop 43, Brooklyn, NY 11203, USA;
- Received August 7, 2013
- Revised February 5, 2014
- Accepted February 14, 2014
- First published March 13, 2014.
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