Unusual identities for QCD at tree-level
  We discuss a set of recently discovered quadratic relations between gauge theory amplitudes. Such relations give additional structural simplifications for amplitudes in QCD. Remarkably, their origin lie in an analogous set of relations that involve also gravitons. When certain gluon helicities are flipped we obtain relations that do not involve gravitons, but which refer only to QCD. 
N.E.J. Bjerrum-Bohr, Poul H. Damgaard, Bo Feng, Thomas Sondergaard
hep-ph