Del Risco Kollerud, Ruby
Blaasaas, Karl Gerhard
Claussen, Bjørgulf
Nafstad, Per
Cannon-Albright, Lisa A
Ruud, Ellen
Wesenberg, Finn
Næss, Øyvind
Article History
Received: 8 September 2017
Revised: 12 December 2017
Accepted: 19 December 2017
First Online: 20 February 2018
Change Date: 20 March 2018
Change Type: Update
Change Details: This paper was modified 12 months after initial publication to switch to Creative Commons licence terms, as noted at publication
Competing interests
: The authors declare no conflict of interest.