ZAVIZION, G. V.; SHKII, N. I. Systems of singularly perturbed degenerate integro-differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 12, p. 1694–1703, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4772. Acesso em: 6 dec. 2025.