Shevelо V. N.; Оdarіch O. N. Some questions of the theory of oscillation (non-oscillation) of the solutions of second order delay differential equations . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 23, n. 4, p. 507–515, 1971. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8584. Acesso em: 5 dec. 2025.