- Correspondence to: E Harville Department of Epidemiology, University of North Carolina, CB#7435, Chapel Hill, NC 27599-7435, USA;
- Accepted January 27, 2004
- First published September 30, 2004.
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.