Heldal, Kari Kulvik
Barregard, Lars
Ellingsen, Dag G.
Funding for this research was provided by:
National Institute of Occupational Health
Article History
Received: 22 June 2015
Accepted: 15 December 2015
First Online: 23 December 2015
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.