Ward Identities for Amplitudes with Reggeized Gluons
  Starting from the effective action of high energy QCD we derive Ward identities for Green's functions of reggeized gluons. They follow from the gauge invariance of the effective action, and allow to derive new representations of amplitudes containing physical particles as well as reggeized gluons. We explicitly demonstrate their validity for the BFKL kernel, and we present a new derivation of the kernel. 
J. Bartels, L. N. Lipatov and G. P. Vacca
hep-th