1. Sheiham A . Is there a scientific basis for six-monthly dental examinations? Lancet 1977; 2: 442–444.
2. Wilson J M G, Jungner G . Principles and practice of screening for disease. Geneva: World Health Organization, 1968.
3. Mandel I D, Zengo A N . Comparative immunology of the oral cavity. In Mergenhagen S E, Sherp H W (eds) Genetic and chemical aspects in caries resistance. pp. 118–137. Washington: US Department of Health, Education and Welfare, 1973.
4. Sheiham A . Why free sugars consumption should be below 15 kg per person per year in industrialised countries: the dental evidence. Br Dent J 1991; 171: 63–65.
5. Cochrane A L . Effectiveness and efficiency: random reflections on health services. London: Nuffield Provincial Hospital Trust, 1972.