Mysterud, Atle
Easterday, William Ryan
Stigum, Vetle Malmer
Aas, Anders Bjørnsgaard
Meisingset, Erling L.
Viljugrein, Hildegunn
Article History
Received: 29 May 2015
Accepted: 9 May 2016
First Online: 16 June 2016
Competing interests
: The authors declare no competing financial interests.