Sulen, André
Lygre, Stein H. L.
Hjelle, Sigrun M.
Hollund, Bjørg E.
Gjertsen, Bjørn T.
Article History
Received: 26 January 2016
Accepted: 13 June 2016
First Online: 6 July 2016
Competing interests
: The authors declare no competing financial interests.