KENZHEBAEV, K. K. A constructive method for finding periodic solutions of differential systems. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 47, n. 4, p. 468–476, 1995. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5444. Acesso em: 5 dec. 2025.