Buchari, U. B., A. M. Muhar, and A. . “The CEA Value Based on Age, Location and Histopathology Degree of Tumor Factors in Colorectal Cancer Patients at Haji Adam Malik General Hospital Medan in 2011-2015”. International Journal of Medical Science and Clinical Invention, vol. 5, no. 5, May 2018, pp. 3848-51, doi:10.18535/ijmsci/v5i5.19.