- Correspondence to Doris G Gammon, Public Health Research Division, RTI International, 3040 E. Cornwallis Road, P.O. Box 12194, Research Triangle Park, NC 27709, USA;
- Received March 11, 2015
- Revised August 14, 2015
- Accepted August 25, 2015
- First published September 10, 2015.
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