1. Richard C. Curtis Hematology Laboratory, Peter Bent Brigham Hospital, and the Department of Medicine, Harvard Medical School, Boston, Mass.
2. Peter Bent Brigham Hospital, Boston, Mass; presently Assistant Professor of Medicine, Department of Medicine, The University of Chicago, Chicago, Ill.
3. Harvard Medical School; Senior Associate in Medicine and Director of the Richard C. Curtis Hematology Laboratory, Peter Bent Brigham Hospital, Boston, Mass.