1. M.R.C. Experimental Haematology Research Unit and Department of Paediatrics, St. Mary's Hospital Medical School, London, England.
2. Member of the Scientific Staff of the Medical Research Council, and Senior Lecturer in Haematology, St. Mary's Hospital Medical School, London, England.
3. Paediatric Unit, St. Mary's Hospital Medical School, London, England.
4. Member of the Scientific Staff of the Medical Research Council, London, England.