Polarization modes of gravitational waves in three-dimensional massive   gravities
  We find polarization modes of gravitational waves in topologically massive and new massive gravities by using the Newman-Penrose formalism where the null real tetrad is necessary to specify gravitational waves. The number of polarization modes is two for the new massive gravity and one for the topologically massive gravity, which is consistent with the metric-perturbation approach. 
Taeyoon Moon and Yun Soo Myung
gr-qc