Tarigan, Elias, et al. “S-Index and APRI Score to Predict Liver Fibrosis Chronic in Hepatitis B and C Patients”. The Indonesian Journal of Gastroenterology, Hepatology, and Digestive Endoscopy, vol. 14, no. 2, Sept. 2013, pp. 64-68, doi:10.24871/142201364-68.