Stenehjem, J S
Kjærheim, K
Bråtveit, M
Samuelsen, S O
Barone-Adesi, F
Rothman, N
Lan, Q
Grimsrud, T K
Article History
Received: 2 August 2014
Revised: 20 February 2015
Accepted: 24 February 2015
First Online: 24 March 2015
Change Date: 28 April 2015
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.