Yakar, Tolga, et al. “The Relationship of Recurrent Aphthous Stomatitis and Helicobacter Pylori, Cytokine Gene Polymorphism and Cobalamin”. Turkish Journal of Gastroenterology, vol. 26, no. 4, Jan. 2015, pp. 304-8, doi:10.5152/tjg.2015.0161.