1. University Medical Center Utrecht; Department of Otorhinolaryngology & Julius Center for Health Sciences and Primary Care; PO Box 85500 Utrecht Netherlands 3508 GA
2. University of Washington; Department of Family Medicine; Box 354696 Seattle WA USA 98195-4696
3. University of Oxford; Nuffield Department of Primary Care Health Sciences; Radcliffe Observatory Quarter Woodstock Road Oxford Oxfordshire UK OX2 6GG
4. Bond University; Centre for Research in Evidence-Based Practice (CREBP); University Drive Robina Gold Coast Queensland Australia 4229
5. Radboud University Nijmegen Medical Centre; Department of Operating Rooms; Hp 630, route 631 PO Box 9101 Nijmegen Netherlands 6500 HB