Non-planar master integrals for the production of two off-shell vector   bosons in collisions of massless partons
  We present the calculation of all non-planar master integrals that are needed to describe production of two off-shell vector bosons in collisions of two massless partons through NNLO in perturbative QCD. The integrals are computed analytically using differential equations in external kinematic variables and expressed in terms of Goncharov polylogarithms. These results provide the last missing ingredient needed for the computation of two-loop amplitudes that describe the production of two gauge bosons with different invariant masses in hadron collisions. 
Fabrizio Caola, Johannes M. Henn, Kirill Melnikov and Vladimir A.   Smirnov
hep-ph