ZERNOV, A. E.; CHAICHUK, O. R. Qualitative investigation of a singular Cauchy problem for a functional differential equation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 57, n. 10, p. 1344–1358, 2005. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3690. Acesso em: 5 dec. 2025.