Fondell E, Lagerros YT, Sundberg CJ, Lekander M, Balter O, Rothman KJ, Balter K. Physical activity, stress, and self-reported upper respiratory tract infection. Med Sci Sports Exerc. 2011 Feb 1;43(2):272-9.
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