Permanency and periodic solutions in models with age structure, delay, and impulsive effect. Neliniini Kolyvannya, [S. l.], v. 13, n. 4, p. 546–555, 2010. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/583. Acesso em: 21 jan. 2026.