A Dual Non-abelian Yang-Mills Amplitude in Four Dimensions
  We derive an explicit formula for the vertex amplitude of dual SU(2) Yang-Mills theory in four dimensions on the lattice, and provide an efficient algorithm (of order j to the fourth power) for its computation. This opens the way for both numerical and analytic development of dual methods, previously limited to the case of three dimensions. 
J. Wade Cherrington, J. Daniel Christensen