Calì, Andrea, Georg Gottlob, and Andreas Pieris. “New Expressive Languages for Ontological Query Answering”. Proceedings of the AAAI Conference on Artificial Intelligence 25, no. 1 (August 4, 2011): 1541-1546. Accessed April 19, 2024. https://ojs.aaai.org/index.php/AAAI/article/view/7957.