Omar Helmy, D., M. Tag El-Sabah, M. Sherif Negm, and M. Armia. “Diagnostic and Pathologic Value of Programmed Death-Ligand 1 Expression in Colon Carcinoma”. Asian Pacific Journal of Cancer Biology, Vol. 5, no. 4, Dec. 2020, pp. 159-66, doi:10.31557/apjcb.2020.5.4.159-166.