1. I.C.S. Swinkels, PhD, NIVEL, Netherlands Institute for Health Services Research, PO Box 1568, 3500 BN, Utrecht, the Netherlands.
2. M.K. Kooijman, PT, MSc, NIVEL, Netherlands Institute for Health Services Research.
3. P.M. Spreeuwenberg, MA, NIVEL, Netherlands Institute for Health Services Research.
4. D. Bossen, PT, PhD, NIVEL, Netherlands Institute for Health Services Research.
5. C.J. Leemrijse, PT, PhD, NIVEL, Netherlands Institute for Health Services Research.
6. C.E. van Dijk, PhD, NIVEL, Netherlands Institute for Health Services Research.
7. R. Verheij, PhD, NIVEL, Netherlands Institute for Health Services Research.
8. D.H. de Bakker, PhD, NIVEL, Netherlands Institute for Health Services Research; and TRANZO (Tilburg University, Scientific Center for Care and Welfare), Tilburg, the Netherlands.
9. C. Veenhof, PT, PhD, NIVEL, Netherlands Institute for Health Services Research.