The Bose-Einstein correlations of pions and kaons emitted from expanding inhomogeneous systems that eventually formed on ultra-relativistic A + A collisions are considered. The structure of the correlation function is obtained using the conception of the system’s lengths of homogeneity. The analysis of the transversal momentum behavior of thelong-, out- andside-interferometry radii is done for radiating sources with relativistic transversal and longitudinal flows moreover for the sources with large temperature gradients. The universal ratios between the momentum slopes of the different interferometry radii of 3D expanding systems are found at large transversal momenta. Simple analytical formula for the interferometry radii are obtained for typical classes of transversal flows.