Funding for this research was provided by:
Text and Data Mining valid from 2019-02-20
Received: 10 August 2018
Accepted: 11 February 2019
First Online: 20 February 2019
Ethics approval and consent to participate
: The Regional Committee for Medical and Health Research Ethics, Norway (REK 4.2007.81) approved the study. The study was conducted in accordance with the ethical principles in the declaration of Helsinki. Written informed consent was obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interest.
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