Hagen, Knut
Stovner, Lars Jacob
Zwart, John-Anker
Article History
Received: 5 February 2020
Accepted: 6 March 2020
First Online: 11 March 2020
Ethics approval and consent to participate
: This study was approved by the Regional Committee for Ethics in Medical Research (2018/2428 REK midt)). The participants have given written informed consent.
: Not applicable.
: None of the authors have any competing interests in the manuscript.