MAKSIMENKO, S. I. On topological spaces with π2 = 0. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 50, n. 8, p. 1144–1146, 1998. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4864. Acesso em: 14 apr. 2025.