1. Molecular Haematology Unit, Department of Haematology, Bristol Royal Infirmary, Bristol, U.K.,
2. Departments of Biochemistry and Biological Structure, University of Washington, Seattle, Washington, U.S.A.,
3. Department of Paediatrics, Princess Margaret Hospital, Swindon, U.K.,
4. National Blood Services Centre, Hospital Kuala Lumpur, Kuala Lumpur, Malaysia