M. AKDOĞAN, E. PARLAK, B. KAYHAN, M. BALK, G. ERSAVAŞTF, and B. ŞAHİN, “Are serum and biliary carcinoembryonic antigen and carbohydrate antigen19-9 determinations reliable for differentiation between benign and malignant biliary disease?”, Turkish Journal of Gastroenterology, vol. 14, no. 3, pp. 181–184, Jan. 2003.