Algebraic characterization of gauge anomalies on a nontrivial bundle
  We discuss the algebraic way of solving the descent equations corresponding to the BRST consistency condition for the gauge anomalies and the Chern--Simons terms on a nontrivial bundle. The method of decomposing the exterior derivative as a BRST commutator is extended to the present case. 
P. John, O. Moritsch, M. Schweda and S.P. Sorella