Lavrenyuk, Y. V., & Sushchanskii, V. I. (2008). Lattice of normal subgroups of a group of local isometries of the boundary of a spherically homogeneous tree. Ukrains’kyi Matematychnyi Zhurnal, 60(10), 1350–1356. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/3249