1. Ahmed R, Chen ISY (eds) (1999) Persistent viral infections. Wiley, Chichester
2. Bartlett MS (1960) The critical community size for measles in the United States. J Royal Stat Soc Series A 123: 37–44
3. Black F (1975) Infectious diseases in primitive societies. Science 187: 515–518
4. Centers for Disease Control (1961–1974) Annual poliomyelitis summaries for the years 1960–1973. Atlanta, Georgia
5. Centers for Disease Control (1977) Poliomyelitis summary, 1974–1976. Atlanta, Georgia