Received: 11 November 2017
Accepted: 19 December 2017
First Online: 6 February 2018
Ethics approval and consent to participate
: The study has been approved by the appropriate ethics committees and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. All persons gave their informed consent prior to their inclusion in the study.
: Not applicable.
: All other authors declare that they have no conflict of interests.
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