1. University Medical Center Utrecht; P.O. Box 85060 3508 AB Utrecht Netherlands
2. Huisartspraktijk Diepenveen; Dorpsstraat 16 Diepenveen Netherlands 7431 CK
3. University Medical Center Utrecht; Julius Center for Health Sciences and Primary Care; PO Box 85500 Utrecht Netherlands 3508 GA
4. University Medical Center Utrecht; Department of Otorhinolaryngology & Julius Center for Health Sciences and Primary Care; PO Box 85500 Internal postal address STR 6.131 Utrecht Netherlands 3508 GA
5. Durham University; School of Medicine and Health, Wolfson Research Institute Queen's Campus, University Boulevard Stockton on Tees UK TS17 6BH
6. Maastricht University; Department of General Practice; Maastricht University Medical Centre, Care and Public Health Research Institute (CAPHRI) PO Box 616 Maastricht Netherlands 6200 MD