1. Final Report of the Global Commission for the Certification of Smallpox Eradication (WHO, Geneva, 1980).
2. Katz, S. L. Pediatrics 71, 653–654 (1983).
3. Centres for Disease Control. Morbidity Mortality Weekly Rep. 32, 1–125 (1983).
4. Noah, N. D. Br. med. J. 289, 1476 (1984).
5. Brook, C. G. D. Br. med. J. 286, 1082–1083 (1983).