Chern-Simons and WZW Anomaly Cancelations Across Dimensions
  The WZW functional in D=4 can be derived directly from the Chern-Simons functional of a compactified D=5 gauge theory and the boundary fermions it supplants. A simple pedagogical model based on U(1) gauge groups illustrates how this works. A bulk-boundary system with the fermions eliminated manifestly evinces anomaly cancelations between CS and WZW terms. 
Christopher T. Hill and Cosmas K. Zachos