1. Institute for Research in Extramural Medicine, Department of General Practice, Vrije Universiteit Medical Center, Amsterdam, the Netherlands
2. Department of Public Health and Primary Care, University of Cambridge, Cambridge, U.K.
3. MacColl Institute for Healthcare Innovation, Center for Health Studies, Group Health Cooperative of Puget Sound, Seattle, Washington
4. Department of Medical Sociology, Universiteit van Maastricht, Maastricht, the Netherlands
5. Dutch Cochrane Centre, Academic Medical Center, Amsterdam, the Netherlands
6. Division of Public Health, Department of General Practice, Academic Medical Center, Amsterdam, the Netherlands