Mangel AW, Fehnel SE. End points in irritable bowel syndrome. Expert Rev Gastroenterol Hepatol. 2011 Jun 1;5(3):293-5.
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