Three Dimensional Lorentz homogeneous spaces and the Petrov   classification
  In this note, we verify the classification of local geometries given by A.Z. Petrov. First, we determine criteria for identifying a given 3D Lorentz homogeneous space in Petrov's classification. Then, we identify all inequivalent 1D subalgebras of all real 4D Lie algebras and determine which of these give rise to a homogeneous space admitting an invariant Lorentz metric. 
Adam Bowers
math-ph math.MP math.RA