Zernov, A. E. (2003). 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, 55(10), 1419-1424. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/4010