NIEMINEN, T. On ultrapseudocompact and related spaces. Annales Fennici Mathematici, [S. l.], v. 3, n. 2, p. 185–205, 1976. DOI: 10.5186/aasfm.1977.0321. Disponível em: https://afm.journal.fi/article/view/134316. Acesso em: 27 apr. 2025.