SOKIL, B. I. On a method for constructing one-frequency solutions of a nonlinear wave equation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 6, p. 782–784, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5708. Acesso em: 5 dec. 2025.