Ahmed, Mian Mashhud, et al. “Declining Prevalence of Helicobacter Pylori Infection- A 13C Urea Breath Test (UBT) Based Study in Symptomatic”. Anwer Khan Modern Medical College Journal, vol. 10, no. 2, Nov. 2019, pp. 121-4, doi:10.3329/akmmcj.v10i2.44120.