Van den Broeck, G., A. Lykov, M. Schleich, and D. Suciu. “On the Tractability of SHAP Explanations”. Proceedings of the AAAI Conference on Artificial Intelligence, vol. 35, no. 7, May 2021, pp. 6505-13, https://ojs.aaai.org/index.php/AAAI/article/view/16806.