- Correspondence to LIB Sikkeland, Department of Respiratory Medicine, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Norway, P.O. Box 4950 Nydalen, Oslo 0424, Norway;
- Received August 11, 2015
- Revised December 17, 2015
- Accepted December 22, 2015
- First published January 19, 2016.
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.