- Correspondence to Roger Hilfiker, School of Health Sciences, HES-SO Valais-Wallis, University of Applied Sciences and Arts Western Switzerland Valais, Rathausstrasse 8, Leukerbad 3954, Switzerland;
- Accepted 12 April 2017
- Published in print 1 September 2017.
- Published online 25 August 2017.
- Published first 19 June 2017.
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