ER’OMENKO, V. O.; ALILUIKO, A. M. Quasiperiodic solutions of degenerate linear systems of second-order ordinary differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 62, n. 6, p. 773–783, 2010. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2908. Acesso em: 5 dec. 2025.