- Correspondence to Dr Youn Ok Lee, Public Health Research Division, RTI International, 3040 Cornwallis Road, Research Triangle Park, NC 27709, USA;
- Received 16 November 2013
- Accepted 3 March 2014
- Published in print 1 July 2015.
- Published online 22 June 2015.
- Published first 11 April 2014.
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