Y. V. Lavrenyuk and V. I. Sushchanskii, “Lattice of normal subgroups of a group of local isometries of the boundary of a spherically homogeneous tree”, Ukr. Mat. Zhurn., vol. 60, no. 10, pp. 1350–1356, Oct. 2008, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3249