1. Molecular Genetics Laboratory, Johns Hopkins University School of Medicine, Baltimore, MD 21231.
2. ICI Pharmaceuticals, Cheshire, United Kingdom SK10 4TG.
3. Department of Pathology, Children's Hospital of Los Angeles, Los Angeles, CA 90027.
4. National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD 20894
5. Department of Biochemistry, Cancer Institute, Tokyo 170, Japan.