KHARCHENKO, A. and YELINSKA, A. DNA typing of the gastric mucosa of patients with chronic duodenal ulcer. Journal of Education, Health and Sport. Online. 30 November 2021. Vol. 11, no. 11, pp. 221-230. [Accessed 27 December 2025]. DOI 10.12775/JEHS.2021.11.11.022.