Text and Data Mining valid from 2020-01-31
Received: 27 February 2019
Accepted: 23 January 2020
First Online: 31 January 2020
Ethics approval and consent to participate
: The study was approved by the Regional Committee for Medical and Health Science Research of South-East Norway (REK no 2010/1511). All participants gave written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.