1. From Institute for Research in Extramural Medicine, Vrije Universiteit Medical Centre, Amsterdam, the Netherlands; Cabrini Medical Centre, Malvern, and Monash University, Melbourne, Victoria, Australia; Erasmus University Rotterdam, Rotterdam, the Netherlands; University of Maastricht, Maastricht, the Netherlands; and Dutch College of General Practitioners and Nivel Netherlands Institute for Health Services Research, Utrecht, the Netherlands.