Funding for this research was provided by:
Text and Data Mining valid from 2018-07-06
Received: 2 February 2018
Accepted: 28 June 2018
First Online: 6 July 2018
Ethics approval and consent to participate
: This study was conducted with the approval of The Regional Committee for Medical and Health Research Ethics in Norway (REC 2012/1665). All study participants have given their informed written consent.
: Not applicable.
: The authors declare that they have no competing interests.
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