ZERNOV, A. E.; KUZINA, Yu. V. Qualitative Investigation of the Singular Cauchy Problem F(t, x, x′) = 0, x(0) = 0. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 12, p. 1720–1723, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4033. Acesso em: 5 dec. 2025.