Horčík, Rostislav, Daniel Fišer, and Álvaro Torralba. “Homomorphisms of Lifted Planning Tasks: The Case for Delete-Free Relaxation Heuristics”. Proceedings of the AAAI Conference on Artificial Intelligence 36, no. 9 (June 28, 2022): 9767-9775. Accessed April 24, 2024. https://ojs.aaai.org/index.php/AAAI/article/view/21212.