“…On the other hand, in R 4 another analogue of the classical Darboux problem in the same domain Ω is given (Bazarbekov [4]). Some different statements on Darboux type problems in R 3 are known also [5,16,17]. Together with P1 its adjoined problem P1 * has been studied for existence of bounded or unbounded solutions for the wave equation in R 3 and R 4 as well as for the Euler-Poisson-Darboux equation [2,11,14,15,18,19,24].…”