Berg, V
Nøst, T H
Skeie, G
Thomassen, Y
Berlinger, B
Veyhe, A S
Jorde, R
Odland, J Ø
Hansen, S
Article History
Received: 12 October 2016
Revised: 17 February 2017
Accepted: 18 April 2017
First Online: 24 May 2017
Competing interests
: The authors declare no conflict of interest.