MITROPOLSKY , Yu. A.; FARKASH , M.; MARTYNYUK , A. A.; MOSHON , P. The 11th International Conference on Nonlineal Oscillations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 40, n. 2, p. 268–269, 1988. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/9132. Acesso em: 17 feb. 2026.