Eyerich, Patrick, and Malte Helmert. “Stronger Abstraction Heuristics Through Perimeter Search”. Proceedings of the International Conference on Automated Planning and Scheduling 23, no. 1 (June 2, 2013): 303–307. Accessed May 26, 2026. https://ojs.aaai.org/index.php/ICAPS/article/view/13604.