RYKHLOV, V. S. Asymptotics of the system of solutions of a general differential equation with parameter. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 1, p. 96–108, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5367. Acesso em: 5 dec. 2025.