Two-Loop Maximal Unitarity with External Masses
  We extend the maximal unitarity method at two loops to double-box basis integrals with up to three external massive legs. We use consistency equations based on the requirement that integrals of total derivatives vanish. We obtain unique formulae for the coefficients of the master double-box integrals. These formulae can be used either analytically or numerically. 
Henrik Johansson, David A. Kosower, Kasper J. Larsen
hep-th hep-ph