- Dr G W Comstock, Training Center for Public Health Research, Box 2067, Hagerstown, MD 21742-2067, USA.
- Accepted February 11, 1997
- First published May 1, 1997.
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.