Koenig, Sven, Maxim Likhachev, Yaxin Liu, and David Furcy. “Incremental Heuristic Search in AI”. AI Magazine 25, no. 2 (June 15, 2004): 99. Accessed October 23, 2019. https://www.aaai.org/ojs/index.php/aimagazine/article/view/1763.