Four-loop verification of algorithm for Feynman diagrams summation in   N=1 supersymmetric electrodynamics
  A method of Feynman diagrams summation, based on using Schwinger-Dyson equations and Ward identities, is verified by calculating some four-loop diagrams in N=1 supersymmetric electrodynamics, regularized by higher derivatives. In particular, for the considered diagrams correctness of an additional identity for Green functions, which is not reduced to the gauge Ward identity, is proved. 
A.B.Pimenov, K.V.Stepanyantz