PINSKY, M. A. Asymptotic Solutions of Linear Differential Equations. CUBO, A Mathematical Journal, [S. l.], v. 3, n. 1, p. 157–183, 2001. Disponível em: https://cubo.ufro.cl/ojs/index.php/cubo/article/view/1750. Acesso em: 19 may. 2024.