  The commonly-known Chern-Simons extension of Einstein gravitational theory is
written in terms of a square-curvature term added to the linear-curvature
Hilbert Lagrangian. In a recent paper, we constructed two Chern-Simons
extensions according to whether they consisted of a square-curvature term added
to the square-curvature Stelle Lagrangian or of one linear-curvature term added
to the linear-curvature Hilbert Lagrangian [Ref. 4]. The former extension gives
rise to the topological extension of the re-normalizable gravity, the latter
extension gives rise to the topological extension of the least-order gravity.
This last theory will be written here in its torsional completion. Then a
consequence for cosmology and particle physics will be addressed.
