Consistency Condition for the Pinch Technique Self-Energies at Two Loops
  A simple and testable necessary condition for the gauge independence of the Pinch Technique self-energies at two loops is discussed. It is then shown that, in the case of the $Z$ and $W$ self-energies, the condition is indeed satisfied by the Papavassiliou-Pilaftsis formulation. 
Kostas Philippides and Alberto Sirlin