BRST analysis of the gauged SU(2) WZW model and Darboux's   transformations
  The four dimensional SU(2) WZW model coupled to elecromagnetism is treated as a constraint system in the context of the BFV approach. We show that the Darboux's transformations which are used to diagonalize the canonical one-form in the Faddeev-Jackiw formalism, transform the fields of the model into BRST invariant ones. The same analysis is also carried out in the case of spinor electrodynamics. 
J.E.Paschalis and P.I.Porfyriadis