- Correspondence to Dr David Faeh, Epidemiology, Biostatistics and Prevention Institute (EBPI), University of Zurich, Hirschengraben 84, 8001 Zurich, Switzerland;
- Received June 16, 2015
- Revised November 27, 2015
- Accepted December 24, 2015
- First published January 20, 2016.
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