Tellex, Stefanie, Thomas Kollar, Steven Dickerson, Matthew R. Walter, Ashis Gopal Banerjee, Seth Teller, and Nicholas Roy. “Approaching the Symbol Grounding Problem With Probabilistic Graphical Models”. AI Magazine 32, no. 4 (December 16, 2011): 64-76. Accessed September 19, 2019. https://www.aaai.org/ojs/index.php/aimagazine/article/view/2384.