1. VU University Medical Center; Department of General Practice, EMGO Institute for Health and Care Research; PO Box 7057 Amsterdam Netherlands 1007 MB
2. Norwegian University of Science and Technology; Unit for Applied Clinical Research, Faculty of Medicine; Trondheim Norway
3. VU University Medical Center; Departments of Epidemiology and Biostatistics, EMGO Institute for Health and Care Research; PO Box 7057 Amsterdam Netherlands 1007 MB
4. EMGO Institute for Health and Care Research, VU University Medical Center; Departments of Epidemiology and Biostatistics; Amsterdam Netherlands