1. Norwegian Back Pain Network, Research Unit, HALOS, University of Bergen, Bergen, Norway,
2. Department of Orthopaedics, Sahlgrenska University Hospital, Göteborg, Sweden
3. Norwegian Back Pain Network, Communication Unit, Ullevål University Hospital, Oslo, Norway
4. Section of Occupational Health and Social Insurance Medicine, Department of General Practice and Community Medicine, University of Oslo, Norway
5. Norwegian Back Pain Network, Research Unit, HALOS, University of Bergen, Bergen, Norway, Department of Biological and Medical Psychology, University of Bergen, Norway
6. Department of Experimental Surgery, Sahlgrenska University Hospital, Göteborg, Sweden
7. Norwegian Gallup AS, Oslo, Norway
8. Hospital of Rehabilitation, Stavern, Norway