AdS-Maxwell Bf Theory As A Model Of Gravity And Bi-Gravity
  This article presents an extended model of gravity obtained by gauging the AdS-Mawell algebra. It involves additional fields that shift the spin connection, leading effectively to theory of two independent connections. Extension of algebraic structure by another tetrad gives rise to the model described by a pair of Einstein equations. 
A. Borowiec, J. Kowalski-Glikman and M. Szczachor
gr-qc hep-th