On the SO(2,1) symmetry in General Relativity
  The role of the SO(2,1) symmetry in General Relativity is analyzed. Cosmological solutions of Einstein field equations invariant with respect to a space-like Lie algebra G_r, with r between 3 and 6 and containing so(2,1) as a subalgebra, are also classified. 
Gaetano Vilasi and Patrizia Vitale