Funding for this research was provided by:
Norges Forskningsråd (221122)
Received: 13 February 2018
Accepted: 5 October 2018
First Online: 22 October 2018
Ethics approval and consent to participate
: The study was approved by the Regional Committee for Medical and Health Research Ethics, Southeast Norway on December 22, 2009 (reference number 2009/2165). Written informed consent was obtained from all participants.
: Not applicable
: The authors declare that they have no competing interests.
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