CHIU, K.-S.; SEPÚLVEDA, I. B. Infinitely many periodic solutions for differential equations involving piecewise alternately advanced and retarded argument. Eurasian Mathematical Journal, [S. l.], v. 16, n. 4, p. 33–44, 2025. Disponível em: https://emj.enu.kz/index.php/main/article/view/875. Acesso em: 7 jan. 2026.