Text and Data Mining valid from 2019-11-14
Received: 21 June 2019
Accepted: 29 October 2019
First Online: 14 November 2019
Ethics approval and consent to participate
: Ethics approval was granted by the Regional Committee for Medical Research ethics, South East Norway [REK2014/2223]. All participants gave their written consent to participate.
: Not applicable.
: The authors declare that they have no competing interests.