Collinear Limits in QCD from MHV Rules
  We consider multi-parton collinear limits of QCD amplitudes at tree level. Using the MHV formalism we specify the underlying analytic structure of the resulting multi-collinear splitting functions. We derive general results for these splitting functions that are valid for specific numbers of negative helicity partons and an arbitrary number of positive helicity partons (or vice versa). 
T.G. Birthwright, E.W.N. Glover, V.V. Khoze and P. Marquard