The Background Field Method: Alternative Way of Deriving the Pinch   Technique's Results
  We show that the background field method (BFM) is a simple way of deriving the same gauge-invariant results which are obtained by the pinch technique (PT). For illustration we construct gauge-invariant self-energy and three-point vertices for gluons at one-loop level by BFM and demonstrate that we get the same results which were derived via PT. We also calculate the four-gluon vertex in BFM and show that this vertex obeys the same Ward identity that was found with PT.} 
Shoji Hashimoto, Jiro Kodaira, Yoshiaki Yasui and Ken Sasaki