IsmoilovA. I., MamanazarovA. O. and UrinovA. K. (2017) “Darboux problem for the generalized Euler – Poisson – Darboux equation”, Ukrains’kyi Matematychnyi Zhurnal, 69(1), pp. 52-70. Available at: http://umj.imath.kiev.ua/index.php/umj/article/view/1675 (Accessed: 22January2021).