Ladіs N. N. Dynamic systems with peculiar trajectories. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 23, n. 2, p. 244–248, 1971. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8508. Acesso em: 5 dec. 2025.