Andréka, Hajnal, and István Németi. “The Generalised Completeness of Horn Predicate-Logic As a Programming Language”. Acta Cybernetica 4, no. 1 (January 1, 1978): 3–10. Accessed April 6, 2025. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3160.