BALLA, E. Sh.; MARKUSH, I. I. On asymptotic solution of the mixed problem for a hyperbolic delay equation . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 23, n. 4, p. 437–453, 1971. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8578. Acesso em: 6 dec. 2025.