Andress, K. M., and Avi Kak. “Evidence Accumulation and Flow of Control in a Hierarchical Spatial Reasoning System”. AI Magazine 9, no. 2 (June 15, 1988): 75. Accessed April 24, 2024. https://ojs.aaai.org/aimagazine/index.php/aimagazine/article/view/677.