Lapin, Morten
Tjensvoll, Kjersti
Oltedal, Satu
Buhl, Tove
Gilje, Bjørnar
Smaaland, Rune
Nordgård, Oddmund
Article History
Received: 11 April 2016
Accepted: 13 June 2016
First Online: 19 July 2016
Competing interests
: The authors declare no competing financial interests.