Estimating of error for averaging method in multifrequency systems with constant delays. Neliniini Kolyvannya, [S. l.], v. 9, n. 2, p. 233–243, 2006. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/394. Acesso em: 21 jan. 2026.