7.Clark LC, Combs GF Jr, Turnbull BW, et al.: Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group. JAMA 276 (24): 1957-63, 1996. http://www.ncbi.nlm.nih.gov/pubmed/8971064
8.Qiao YL, Dawsey SM, Kamangar F, Fan JH, Abnet CC, Sun XD, Johnson LL, Gail MH, Dong ZW, Yu B, Mark SD, Taylor PR. Total and cancer mortality after supplementation with vitamins.
9.Taylor PR, Li B, Dawsey SM, Li JY, Yang CS, Guo W, Blot WJ. Prevention of esophageal cancer: the nutrition intervention trials in Linxian, China. Linxian Nutrition Intervention Trials Study Group. Cancer Res. 1994 Apr 1;54(7 Suppl):2029s-2031s. http://www.ncbi.nlm.nih.gov/pubmed/8137333