Kilpeläinen, Pekka, and Heikki Mannila. “Generation of Test Cases for Simple Prolog Programs”. Acta Cybernetica 9, no. 3 (January 1, 1990): 235–246. Accessed April 10, 2025. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3370.