Seiref, Shawn, Tamir Jaffey, Margarita Lopatin, and Ariel Felner. “Solving the Watchman Route Problem on a Grid With Heuristic Search”. Proceedings of the International Conference on Automated Planning and Scheduling 30, no. 1 (June 1, 2020): 249-257. Accessed February 27, 2021. https://ojs.aaai.org/index.php/ICAPS/article/view/6668.