Funding for this research was provided by:
Bundesministerium für Bildung und Forschung (16KT1236)
Article History
Received: 15 January 2018
Accepted: 9 May 2018
First Online: 24 May 2018
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: This article does not contain any studies with human participants or animals performed by any of the authors.
: Informed consent was obtained from all individual participants included in the study.