- Correspondence to Dr Judy A Stevens, National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, 4770 Buford Highway NE, Mailstop F-62, Atlanta, GA 30341, USA;
- Received August 17, 2012
- Revised November 4, 2012
- Accepted November 27, 2012
- First published January 15, 2013.
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