Mysterud, Atle http://orcid.org/0000-0001-8993-7382
Jore, Solveig
Østerås, Olav
Viljugrein, Hildegunn
Article History
Received: 5 July 2017
Accepted: 27 October 2017
First Online: 24 November 2017
Competing Interests
: The authors declare that they have no competing interests.