Lavrenyuk, S. P., and P. Ya. Pukach. “Mixed Problem for a Nonlinear Hyperbolic Equation in a Domain Unbounded With Respect to Space Variables”. Ukrains’kyi Matematychnyi Zhurnal 59, no. 11 (November 25, 2007): 1523–1531. Accessed March 29, 2023. https://umj.imath.kiev.ua/index.php/umj/article/view/3408.