AGARWAL, P.; WAN-TONG, Li. Interval Oscillation Criteria for Second-Order Nonlinear Differential Equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 53, n. 9, p. 1161–1173, 2001. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4334. Acesso em: 27 apr. 2025.