On the ambiguities in the effective action in Lorentz-violating gravity
  We investigate the occurrence of ambiguities for Lorentz-violating gravitational Chern-Simons term. It turns out that this term is accompanied by a coefficient depending on an undetermined parameter, due to an arbitrariness in the choice of the conserved current. 
M. Gomes, T. Mariz, J. R. Nascimento, E. Passos, A. Yu. Petrov, A. J.   da Silva