A. E. Zernov, “Qualitative Investigation of the Singular Cauchy Problem $\sum\limits_{k = 1}^n {(a_{k1} t + a_{k2} x)(x’)^k = b_1 t + b_2 x + f(t,x,x’),x(0) = 0}$”, Ukr. Mat. Zhurn., vol. 55, no. 10, pp. 1419–1424, Oct. 2003, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4010