1. Acheson, E.D. (1968). Journal of the Royal Statistical Society, Series A, 131, 9–12.
2. Ashley, J.S.A. (1972). British Journal of Preventive and Social Medicine, 26, 135–147.
3. Benjamin, B. (1965). The Hospital, 61, 221–224.
4. Benjamin, B. (1977). Journal of the Royal Statistical Society, Series A, 140, 366–376.
5. Goldacre, M.J., Gatherer, A. (1977a). The Hospital and Health Services Review, 73, 14–16.