Multiloop Calculations in the String-Inspired Formalism: The Single   Spinor-Loop in QED
  We use the worldline path-integral approach to the Bern-Kosower formalism for developing a new algorithm for calculation of the sum of all diagrams with one spinor loop and fixed numbers of external and internal photons. The method is based on worldline supersymmetry, and on the construction of generalized worldline Green functions. The two-loop QED $\beta$ -- function is calculated as an example. 
Michael G. Schmidt and Christian Schubert