SHCHITOV, I. N. Asymptotic expansions of solutions to singularly perturbed systems. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 4, p. 552–560, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5842. Acesso em: 5 dec. 2025.