DANILOV, V. Ya.; MARTYNYUK, D. I.; PAN'KOV, V. G. Second bogolyubov theorem for systems of difference equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 4, p. 464–475, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5311. Acesso em: 5 dec. 2025.