1. The Research Institute of the Norwegian Medical Association, Oslo, Norway,
2. The Norwegian Electronic Health Library, The Norwegian Knowledge Centre for The Health Services, Norway, Department of Public Health and General Practice, Norwegian University of Science and Technology, Trondheim, Norway, Department of Public Health and General Practice, University of Oslo, Norway
3. The Research Institute of the Norwegian Medical Association, Oslo, Norway, Institute of Health Management and Health Economics, University of Oslo, Norway