KOSTIN, A. V.; SHCHEGOLEV, S. A. On solutions of a second-order quasilinear differential system representable by Fourier series with slowly varying parameters. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 50, n. 5, p. 654–664, 1998. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4903. Acesso em: 5 dec. 2025.