Silalahi, Ester Morina, Lukman Hakim Zain, and Rustam Effendi. “Serum Carcinoembryonic Antigen Tends to Decrease in Poorly-Differentiated Colorectal Cancer”. Universa Medicina 32, no. 3 (December 7, 2013): 165–171. Accessed March 29, 2024. https://univmed.org/ejurnal/index.php/medicina/article/view/90.