- Correspondence to Ann Kristin Sjaastad, Norwegian University of Science and Technology, Department of HSE, Trondheim N-7491, Norway;
- Accepted August 6, 2009
- First published February 17, 2010.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.