Two-Loop Corrections to Fermion Pair Production Vertices
  Recent results on the entirely analytic calculation of second order corrections to massive quark pair production vertices induced by light quark flavours are reviewed. Based on the method presented in this talk the second order effects of the insertion of any massless one-loop vacuum polarization into the gluon line of the first order diagrams can be determined. The behaviour of the corrections at threshold for vector and axial-vector current induced massive quark production is discussed. 
A.H. Hoang (Uni. Karlsruhe, Germany)