Received: 22 November 2017
Accepted: 30 August 2018
First Online: 11 September 2018
Ethics approval and consent to participate
: All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation and with the Helsinki Declaration of 1975, as revised in 2000. The study was approved by the Ethics Committee Freiburg, Germany on 01.07.2014. Registry number: 306/14.
: Not applicable.
: The authors declare that they have no competing interests.
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