1. Division of Hematology, Department of Medicine, Stanfard University School of Medicine, Stanford, Calif.
2. Haile Sellassie University, Gondar, Ethiopia; Fellow in Hematology supported by Grant No. 104 from the Daland Fund of the American Philosophical Society.
3. Stanford University School of Medicine, Stanford, Calif.
4. Division of Hematology, Stanford University School of Medicine, Stanford, Calif.