  We present analytical potential-density pairs in three dimensions for the
gravitational field of galaxies, obtained by thickening the multipolar
expansion up to the quadrupole term. These may be interpreted as
generalizations of the Miyamoto and Nagai potential-density pairs. With a
suitable restriction on the possible values of the multipole moments, the
density distributions are positive and monotone decreasing functions of the
radial and axial coordinates.
