1. Rodu, B. Am. J. med. Sci. 308, 32–34 (1994).
2. Cullen, J. W. et al. Pub. Hlth. Rep. 101, 355–373 (1986).
3. Winn, D. M. et al. New Engl. J. Med. 304, 745 (1981).
4. Garfinkel, L. NCI Monogrs. 67, NIH publ. no. 85–2713, 49–52 (1985).
5. Cole, P. & MacMahon, B. Br. J. Prev. Soc. Med. 25, 242–244 (1971).