Funding for this research was provided by:
Deutsche Forschungsgemeinschaft (WO 1746/1-1)
Innovative Medicine Initiative Joint Undertaking (115737-2)
Received: 13 October 2017
Accepted: 30 April 2018
First Online: 30 May 2018
Ethics approval and consent to participate
: Not applicable.
: MW is a member of the editorial board of BMC research methodology. SR, MvC and MS declare no competing interests.
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