1. National Cancer Institute, Bethesda, Maryland 20205
2. University of Cape Town Medical School, Cape Town, South Africa
3. Georgetown University Hospital, Washington, D.C. 20007
4. South African Blood Transfusion Service, Johannesburg, South Africa
5. Naval Medical Research Institute, Bethesda, Maryland 20014
6. Navy Medical Research Unit No. 3, Cairo, Egypt, FPO New York 09527
7. International Agency for Research in Cancer, Lyon, France
8. University of Ghana, Medical School, Accra, Ghana
9. Institute Salah Azaiz, Bab Saadoun, Tun-is, Tunisia
10. Laboratory of Tumor Cell Biology, National Cancer Institute