Multilayer spherical stellar cluster with uniform density
  Various solutions of the kinetic equation for the equilibrium of a
gravitating sphere of uniform density with a quadratic gravitational potential
and a linear dependence of gravitational force on radius are examined. New
analytic solutions are obtained for a uniform sphere with a hollow spherical
volume and central mass inside the sphere. Solutions are also obtained for an
arbitrary number of spherical layers with the same density, but with different
equilibrium distribution functions.
