EFENDIEV, V. V. Averaging of Systems with Slow Variables. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 54, n. 9, p. 1265–1275, 2002. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4164. Acesso em: 5 dec. 2025.