Lуkоvа О. В. Extension of a theorem of N. N. Bogolyubov to the case of a Hilbert space . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 18, n. 5, p. 53–59, 1966. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8440. Acesso em: 17 apr. 2025.