H. Purbayu, P. B. Setiawan, I. A. Nusi, P. Adi, and H. O. Kusumobroto, “Validation of 13C-urea Breath Test for the Diagnosis of Helicobacter pylori Infection Among Dyspeptic Patients at Dr Soetomo Hospital Surabaya”, InaJGHE, vol. 8, no. 3, pp. 76–79, Jan. 2007.