Funding for this research was provided by:
Norges Forskningsråd (222100)
Text and Data Mining valid from 2018-11-08
Received: 22 September 2017
Accepted: 31 October 2018
First Online: 8 November 2018
Ethics approval and consent to participate
: This research project is approved by the Norwegian Data Protection Authority, as well as The Regional Committees for Medical and Health Research Ethics (REC), region REC South East (application reference 2013/821/REK sør-øst D). The unique personal identification number and variable categories which could potentially be used for identifying individuals were removed from the data before made available for research, implying that individual consent to participate is not required according to the national legislation (ExternalRef removed).
: Not applicable
: The author declares that he has no competing interests.
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