Urinov, A. K., and A. B. Okboev. “Modified Cauchy Problem for One Degenerated Hyperbolic Equation of the Second Kind”. Ukrains’kyi Matematychnyi Zhurnal, vol. 72, no. 1, Jan. 2020, pp. 100-18, https://umj.imath.kiev.ua/index.php/umj/article/view/656.