ÖZDEN, Ali, et al. “THE PREVALENCE OF HELICOBACTER PYLORI IN PATTENTS WITH UPPER GASTROINTESTINAL COMPLAINTS”. Turkish Journal of Gastroenterology, vol. 3, no. 1, Jan. 1992, pp. 102-8, https://www.turkjgastroenterol.org/index.php/tjg/article/view/62.