A. Shirzad, GAUGE-SYMMETRY IN LAGRANGIAN FORMULATION AND SCHWINGER MODELS, Journal of physics. A, mathematical and general, 31(11), 1998, pp. 2747-2760
A systematic method is presented for processing the equations of motio
n of a singular Lagrangian that, in principle, has all dynamical degre
es of freedom together with the Lagrangian constraints and a number of
identities between the equations of motion. Then, using these identit
ies one can find the complete set of gauge transformations of the syst
em. Different types of Schwinger model are considered as examples and
the related gauge transformations are derived.