Second-Order Radiative Corrections to the Axial Vector Anomaly
  We re-examine the historically important decay of the neutral pion into two photons. Schwinger's Equivalence Theorem is confirmed. We then consider radiative corrections to the famous Adler-Bell-Jackiw (ABJ) anomaly. The result depends crucially on a physically motivated regularization scheme. Our approach is largely based on Schwinger's source (dispersion) method. 
Walter Dittrich (Tubingen U.)