Tha averaging of some boundary value problems for systems of differential equations with a variable delay. Neliniini Kolyvannya, [S. l.], v. 1, n. 2, p. 152–156, 1998. Disponível em: https://nosc.imath.kiev.ua/index.php/nosc/article/view/32. Acesso em: 12 apr. 2026.