Jaipong, Pradthana, and Wanchai Tapanyo. “Connectivity of Suborbital Graphs for the Congruence Subgroups of the Extended Modular Group”. Communications in Mathematics and Applications 8, no. 3 (December 30, 2017): 345–358. Accessed May 2, 2024. http://www.rgnpublications.com/journals/index.php/cma/article/view/549.