- Correspondence to Professor Daniel Kotz, Addiction Research and Clinical Epidemiology Unit, Medical Faculty of the Heinrich-Heine, University Düsseldorf, Institute of General Practice, Düsseldorf 40225, Germany;
- Received January 26, 2017
- Revised March 17, 2017
- Accepted April 4, 2017
- First published May 4, 2017.
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