MHV-Vertices for Gravity Amplitudes
  We obtain a CSW-style formalism for calculating graviton scattering amplitudes and prove its validity through the use of a special type of BCFW-like parameter shift. The procedure is illustrated with explicit examples. 
N. E. J. Bjerrum-Bohr, David C. Dunbar, Harald Ita, Warren B. Perkins   and Kasper Risager