The approximation of a system of differential-difference equations by a system of ordinary differential equations. Neliniini Kolyvannya, [S. l.], v. 2, n. 1, p. 42–49, 1999. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/39. Acesso em: 22 jan. 2026.