Jekti, Dwi Sulistya Dyah, et al. “The Absence of Urease Enzymatic Activity of Helicobacter Pylori Coccoid Form”. The Indonesian Journal of Gastroenterology, Hepatology, and Digestive Endoscopy, vol. 9, no. 2, Jan. 2008, pp. 35-41, doi:10.24871/92200835-41.