Rettedal, S
Löhr, I H
Bernhoff, E
Natås, O B
Sundsfjord, A
Øymar, K
Article History
Received: 27 January 2015
Revised: 21 April 2015
Accepted: 1 June 2015
First Online: 9 July 2015
Competing interests
: The authors declare no conflict of interest.