Meral AKDOĞAN, et al. “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, July 2019, pp. 181-4, https://tjg.avesjournals.com/index.php/tjg/article/view/1857.