Ørbo, Anne
Arnes, Marit
Lyså, Lena Myreng
Borgfelt, Christer
Straume, Bjørn
Article History
Revised: 4 June 2016
Accepted: 12 July 2016
First Online: 18 August 2016
Change Date: 6 September 2016
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.