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Article History

Received: 1 September 2018

Accepted: 17 February 2019

First Online: 26 February 2019

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: Scientific evaluation of this research database received a positive assessment by the Central Ethics Commission of the University of Witten/Herdecke (no. 201/2015). As data were anonymised informed consent was not obtainable and thus waived by the ethics committee.

: Not applicable.

: The authors declare that they have no competing interests.

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