Article History
Received: 12 April 2017
Accepted: 15 January 2018
First Online: 25 January 2018
Ethics approval and consent to participate
: The ethics committee of the Friedrich Alexander Universität (FAU) Erlangen Nürnberg did not have any ethical or legal concerns about the retrospective analysis of the data reported in this manuscript.
: Not applicable
: The authors declare that they have no competing interests.
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