Căzănescu, Virgil Emil, and Rodica Ceterchi. “Initial and Final Congruences”. Acta Cybernetica 10, no. 3 (January 1, 1992): 199–215. Accessed April 15, 2025. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3406.