Cueto HT, Riis AH, Hatch EE, Wise LA, Rothman KJ, Sørensen HT, Mikkelsen EM. Folic acid supplementation and fecundability: a Danish prospective cohort study. Eur J Clin Nutr. 2016 Jan;70(1):66-71. doi: 10.1038/ejcn.2015.94
Glass RL, Rothman KJ, Espinal F, Velez H, Smith NJ. Prevalence of human dental caries and water-borne trace metals. Arch Oral Biol. 1973 Sep;18(9):1099-104. doi: 10.1016/0003-9969(73)90083-6