Text and Data Mining valid from 2018-11-13
Received: 31 May 2018
Revised: 11 October 2018
Accepted: 1 November 2018
First Online: 13 November 2018
Compliance with ethical standards
: The project was approved by the Ethics Committee of the canton of Bern (KEK 236/15).
: The authors declare that they have no conflict of interest.