Ardianto, T., W. Warsinggih, and A. Seweng. “Correlation Between Histopathological Grading and Appearance of Obstruction With Level of Carsino-Embryonic Antigen (CEA) in Colorectal Carcinoma”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 45, no. 2, Apr. 2019, pp. 31-38, https://gssrr.org/index.php/JournalOfBasicAndApplied/article/view/9932.