  We present some integral transform that allows to obtain solutions of the
generalized Tricomi equation from solutions of a simpler equation. We used in
[13,14],[41]-[46] the particular version of this transform in order to
investigate in a unified way several equations such as the linear and
semilinear Tricomi equations, Gellerstedt equation, the wave equation in
Einstein-de Sitter spacetime, the wave and the Klein-Gordon equations in the de
Sitter and anti-de Sitter spacetimes.
