Shin, Kilho, and Dave Shepard. “Morphism-Based Learning for Structured Data”. Proceedings of the AAAI Conference on Artificial Intelligence 34, no. 04 (April 3, 2020): 5767-5775. Accessed April 11, 2021. https://ojs.aaai.org/index.php/AAAI/article/view/6033.