Inci, F., and F. Karatas. “The Relationship of Preoperative and Postoperative Serum CEA and CA 19-9 Levels With Tumor Localization, Stage and Overall Survival in Patients With Colorectal Cancer”. Annals of Medical Research, vol. 28, no. 4, May 2021, pp. 0726-32, http://www.annalsmedres.org/index.php/aomr/article/view/465.