Lykova О. B. Development of the Bogolyubov-Mitropolsky method of integral varieties. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 1, p. 33–46, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2318. Acesso em: 6 dec. 2025.