1. Department of Medicine; Rehabilitation Teaching and Research Unit; Wellington School of Medicine and Health Sciences, University of Otago PO Box 7343 Wellington South Wellington New Zealand
2. Norwegian University of Sport and Physical Education; PB 4014 Ulleval Hageby Oslo Norway 0306
3. University Hospital Maastricht; Department of Urology; PO Box 5800 Maastricht Netherlands 6202 az
4. Dutch National Institute of Allied Health Professions; Postbus 1161 Amersfoort Netherlands 3800 BD
5. Maastricht University; Department of Epidemiology; P.O. Box 616 Maastricht Netherlands 6200 MD