Key points are not available for this paper at this time.
New boundary conditions on the Einstein-Rosen-Bondi gravitational-wave metrics yield closed inhomogeneous universes which solve Einstein's vacuum field equations exactly. Space sections of these universes have either the three-sphere topology S^3 or the wormhole (hypertorus) topology S^1S^2.
Robert H. Gowdy (Mon,) studied this question.