MitropolskiyY. A., KhomaN. H., & KhomaS. G. (2000). Smooth Solution of the Dirichlet Problem for a Quasilinear Hyperbolic Equation of the Second Order. Ukrains’kyi Matematychnyi Zhurnal, 52(7), 931-935. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/4492