“…The Tricomi problem for a mixed elliptic-hyperbolic equation in threedimensional space using the method of integral Fourier transform was first studied in [3]. After this work, a number of works appeared in which boundary value problems for various elliptic-huperbolic equations in three-dimensional domains were considered (see, for example, [4], [5], [6], [7], [8], [9], [10], [11], [12]).…”