Funding for this research was provided by:
Schleswig-Holstein (Land Schleswig-Holstein within the funding programme Open Access Publikationsfonds)
Received: 23 April 2018
Accepted: 26 July 2018
First Online: 16 August 2018
Ethics approval and consent to participate
: The ethics committee of the medical faculty of the University of Tübingen approved the study and all participants gave written informed consent prior to participation.
: This submission is made in agreement with my colleagues who were fully involved in the study and preparation of the manuscript. Each of the authors has read and concurs with the content in the final manuscript.
: The authors declare that they have no competing interests.
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