Funding for this research was provided by:
Bundesministerium für Bildung und Forschung (FKZ033L145D)
Open Access Fund of the Leibniz Association
Received: 18 January 2019
Accepted: 17 July 2019
First Online: 10 September 2019
Ethics approval and consent to participate
: Before interviews were conducted, an interview consent form was provided to all participants. Each participant signed a consent letter in order to participate in the interview. Ethics approval is not applicable.
: The authors consent to publication.
: The authors declare that they have no competing interests.