Hansen, Bent-Are
Bruserud, Øyvind
Article History
Received: 8 February 2018
Accepted: 13 March 2018
First Online: 27 March 2018
Ethics approval and consent to participate
: No approval is required.
: No consent is required.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.