Two-loop QCD Corrections to the Heavy Quark Form Factors: the Vector   Contributions
  We present closed analytic expressions of the electromagnetic vertex form factors for heavy quarks at the two-loop level in QCD for arbitrary momentum transfer. The calculation is carried out in dimensional regularization. The electric and magnetic form factors are expressed in terms of 1-dimensional harmonic polylogarithms of maximum weight 4. 
W. Bernreuther, R. Bonciani, T. Gehrmann, R. Heinesch, T. Leineweber,   P. Mastrolia, and E. Remiddi