GURARII, V.; KATSNELSON, V.; MATSAEV, V.; STEINER, J. The Stokes structure in asymptotic analysis II: from differential equation to Stokes structure. Математическая физика, анализ, геометрия, Харків, Україна, v. 9, n. 3, p. 326–338, 2002. Disponível em: http://mag.ilt.kharkiv.ua/index.php/mag/article/view/m09-0326e. Acesso em: 13 чер. 2024.