  We consider the double-soft limit of a generic QCD process involving massless
partons and integrate analytically the double-soft eikonal functions over the
phase-space of soft partons (gluons or quarks) allowing for an arbitrary
relative angle between the three-momenta of two hard massless radiators. This
result provides one of the missing ingredients for a fully analytic formulation
of the nested soft-collinear subtraction scheme recently proposed by some of
us.
