- Correspondence to: Dr M Hooiveld Department of Epidemiology and Biostatistics (133), Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB, Netherlands;
- Accepted 20 April 2006
- Published online 18 July 2006.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.