The No-Triangle Hypothesis for N=8 Supergravity
  We study the perturbative expansion of N=8 supergravity in four dimensions from the viewpoint of the ``no-triangle'' hypothesis, which states that one-loop graviton amplitudes in N=8 supergravity only contain scalar box integral functions. Our computations constitute a direct proof at six-points and support the no-triangle conjecture for seven-point amplitudes and beyond. 
N. E. J. Bjerrum-Bohr, David C. Dunbar, Harald Ita, Warren B. Perkins   and Kasper Risager