Classical BRST charges in reducible BRST-anti-BRST theories
  We give a solution to the classical master equation of the Hamiltonian BRST-anti-BRST quantization scheme in the case of reducible gauge theories. Our approach does not require redefining constraints or reducibility functions. Classical BRST observables are also constructed. 
A.V. Bratchikov
math-ph hep-th math.MP