UK Ministry of Agriculture, Fisheries and Food advice as reported in the Sunday Times, 1999.

Willet, W.C., 1994. Micronutrients and cancer risk. Am J. Clin. Nutr., 59, (suppl), 1162S-5S. See also: Willett, Walter C., Colditz, Graham A. and Mueller, Nancy A., 1996. Strategies for Minimising Cancer Risk. Scientific American, Special Issue, What you need to know about Cancer, September, 275, 3, 88–95.