GRIGORCHUK, R. I.; KRAVCHENKO, R. On the rigidity of rank gradient in a group of intermediate growth. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 70, n. 2, p. 165–176, 2018. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1548. Acesso em: 5 dec. 2025.