An asymptotic expansion of solutions of a singularly perturbed boundary-value problem. Neliniini Kolyvannya, [S. l.], v. 7, n. 2, p. 155–168, 2004. Disponível em: https://nosc.imath.kiev.ua/index.php/nosc/article/view/299. Acesso em: 12 apr. 2026.