CHECHIN, S. A. On one property of hypercyclic groups. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 47, n. 3, p. 436–438, 1995. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5439. Acesso em: 7 apr. 2025.