ZERNOV, A. E. Qualitative Investigation of the Singular Cauchy Problem $\sum\limits_{k = 1}^n {(a_{k1} t + a_{k2} x)(x’)^k = b_1 t + b_2 x + f(t,x,x’),x(0) = 0}$. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 10, p. 1419–1424, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4010. Acesso em: 5 dec. 2025.