YAKOVETS, V. P. Construction of Asymptotic Solutions of Linear Systems of Differential Equations with Two Small Parameters. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 7, p. 961–976, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3971. Acesso em: 6 dec. 2025.