Janin, David, and Giacomo Lenzi. “On the Logical Definability of Topologically Closed Recognizable Languages of Infinite Trees”. COMPUTING AND INFORMATICS 21, no. 3 (February 21, 2012): 185–203. Accessed April 19, 2024. https://www.cai.sk/ojs/index.php/cai/article/view/495.