Article History
Received: 9 July 2018
Accepted: 27 November 2018
First Online: 11 December 2018
Compliance with ethical standards
: This study was carried out in compliance with the project plan, the current version of the Helsinki Declaration, and Swiss law. The research project was approved by the Cantonal Commission for Ethics in Zurich in December 2016 (BASEC-NR. 2016-01372).
: The authors declare that they have no conflict of interest.