1. Coupland M A, Coupland A I . Seasonality, incidence, and sex distribution of cleft lip and palate births in Trent region, 1973-1982. Cleft Palate J 1988; 25: 33–37.
2. Gregg T, Boyd D, Richardson A . The incidence of cleft lip and palate in Northern Ireland from 1980-1990. Br J Orthod 1994; 21: 387–392.
3. Albery E H, Hathorn I S, Pigott R W . Cleft lip and palate: a team approach. Bristol: Wright, 1986.
4. Shaw W C, Williams A C, Sandy J R, Devlin H B . Minimum standards for the management of cleft lip and palate: efforts to close the audit loop. Ann R Coll Surg Engl 1996; 78: 110–114.
5. Clinical Standards Advisory Group Report on Cleft Lip and/or Palate. London: The Stationery Office, 1998.