On asymptotic integration of a linear system of differential equations with a small parameter at some of the derivatives. Neliniini Kolyvannya, [S. l.], v. 12, n. 2, p. 208–234, 2009. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/521. Acesso em: 21 jan. 2026.