- Correspondence to Dr Karyn Heavner, Drexel University School of Public Health, Department of Environmental and Occupational Health, Nesbit Hall, 3215 Market St, Philadelphia, PA 19104, USA;
- Received June 13, 2013
- Revised December 8, 2013
- Accepted December 9, 2013
- First published January 27, 2014.
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