A. H. Al-dujaili, W. F. Al-Taei, K. M. Turky, and G. H. Al-Ubaidi, “Comparative study of CA19-9 levels as tumor marker in sera and tissues of patients with stomach, colon and rectum cancers”, JFacMedBagdad, vol. 51, no. 2, pp. 223–226, Jul. 2009, doi: 10.32007/jfacmedbagdad.5121218.