Britt (DiBenedetti) DM, Collins FL, Cohen LM. Cigarette smoking and chewing gum use among college students. J Appl Biobehav Res. 2007 Jun 4;4(2):85-90. doi: 10.1111/j.1751-9861.1999.tb00057.x
Spector D, Anthony M, Alexander D, Arab L. Soy consumption and colorectal cancer. Nutr Cancer. 2003;47(1):1-12.