Perturbative Gravity and Twistor Space
  The recent progress in computing gauge theory amplitudes can be extended, in many cases, to theories incorporating gravity. This has improved our understanding of the perturbative expansion of N=8 supergravity supporting the ``no-triangle hypothesis'' that N=8 one-loop amplitudes may be expressed in terms of scalar box integral functions. 
N. E. J. Bjerrum-Bohr, David C. Dunbar and Harald Ita