1. Department of Radiation Oncology; The Vanderbilt Clinic, Vanderbilt University Medical Center; Nashville Tennessee U.S.A.
2. Department of Radiation Physics; The University of Texas M. D. Anderson Cancer Center; Houston Texas U.S.A.
3. Oregon Health & Science University; Portland Oregon U.S.A.
4. Department of Radiation Oncology; The University of Texas Southwestern Medical Center; Dallas Texas U.S.A.
5. Department of Radiation Oncology; Thomas Jefferson University Hospital; Philadelphia Pennsylvania U.S.A.
6. Ottawa Regional Cancer Center; Ottawa Ontario K1H 1C4 Canada
7. Department of Biomathematics; The University of Texas M. D. Anderson Cancer Center; Houston Texas U.S.A.
8. Section of Medical Oncology; Rush-Presbyterian-St. Luke's Medical Center; Chicago Illinois U.S.A.
9. University of Pittsburgh Cancer Institute; Pittsburgh Pennsylvania U.S.A.