The Light Front Gauge Propagator: The Status Quo
  At the classical level, the inverse differential operator for the quadratic term in the gauge field Lagrangian density fixed in the light front through the multiplier (nA)^2 yields the standard two term propagator with single unphysical pole of the type (kn)^-1. Upon canonical quantization on the light-front, there emerges a third term of the form (kn^(mu)n^(nu))(kn)^-2. This third term in the propagator has traditionally been dropped on the grounds that is exactly cancelled by the "instantaneous" term in the interaction Hamiltonian in the light-front. Our aim in this work is not to discuss which of the propagators is the correct one, but rather to present at the classical level, the gauge fixing conditions that can lead to the three-term propagator. 
A.T. Suzuki and J.H.O. Sales