1. Department of Radiation Medicine, Georgetown University School of Medicine, Vincent T. Lombardi Cancer Center, Washington, DC 20007.
2. Laboratory of Human Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
3. Michael Reese Hospital, University of Chicago Center for Radiation Therapy, Pritzker School of Medicine, University of Chicago, Chicago, IL 60637.