Funding for this research was provided by:
Bundesministerium für Bildung und Forschung (16SV7789K)
Received: 2 November 2017
Accepted: 15 February 2018
First Online: 21 February 2018
Ethics approval and consent to participate
: The study received ethics approval by the ethics committee of the University of Bielefeld, Germany. Participants were informed about general study content and anonymity on the first page of the online survey. They have to check the consent box in order to participate.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.