1. Public Health Service of Haaglanden; Epidemiology; The Hague Netherlands
2. Pulmonary Rehabilitation Centre Hornerheide; Hornerheide 1 P.O. Box 4080 AB Haelen Netherlands 6080
3. VU University Amsterdam; Department of Health Sciences, EMGO+ Institute for Health and Care Research; PO Box 7057 Amsterdam Netherlands 1007 MB
4. University of Nijmegen and Maastricht; Centre for Quality of Care Research; P.O. Box 9101 Nijmegen Netherlands 6500 HB
5. CAPHRI School for Public Health and Primary Care, Maastricht University Medical Centre; Department of Family Medicine; Maastricht Netherlands