Funding for this research was provided by:
Deutscher Akademischer Austauschdienst (NA)
Dr. Hermann Eiselen Ph.D. Grant (NA)
Received: 13 December 2018
Accepted: 28 June 2019
First Online: 1 August 2019
Ethics approval and consent to participate
: An ethical clearance certificate was obtained from the University of Bonn. All participants were asked for their consent to participate in the survey.
: The authors give consent for publication.
: The authors declare that they have no competing interest.