Boichuk О. A.; SHEHDA, L. M. Degenerate nonlinear boundary-value problems. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 61, n. 9, p. 1174–1188, 2009. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3090. Acesso em: 5 dec. 2025.