1.
Kovach YI. Theorem of the «fork» in Cauchy’s problem for nonlinear partial differential equations of higher orders. Ukr. Mat. Zhurn. [Internet]. 1966 Aug. 31 [cited 2025 Dec. 6];18(5):23-35. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/8438