Diagrammatic proof of the BCFW recursion relation for gluon amplitudes   in QCD
  We present a proof of the Britto-Cachazo-Feng-Witten tree-level recursion relation for gluon amplitudes in QCD, based on a direct equivalence between BCFW decompositions and Feynman diagrams. We demonstrate that this equivalence can be made explicit when working in a convenient gauge. We exhibit that gauge invariance and the particular structure of Yang-Mills vertices guarantees the validity of the BCFW construction. 
Petros D. Draggiotis, Ronald H.P. Kleiss, Achilleas Lazopoulos and   Costas G. Papadopoulos