Text and Data Mining valid from 2019-02-15
Received: 14 August 2018
Accepted: 25 January 2019
First Online: 15 February 2019
Compliance with Ethical Standards
: The authors declare that they have no competing interests.
: The study was approved by the Ethics Committee of the University of Graz, Austria (reference number GZ. 39/69/63 ex 2016/17). The study is in accordance with the ethical standards of the Declaration of Helsinki.
: All participants gave written informed consent.