Relating Green's Functions in Axial and Lorentz Gauges using Finite   Field-Dependent BRS Transformations
  We use finite field-dependent BRS transformations (FFBRS) to connect the Green functions in a set of two otherwise unrelated gauge choices. We choose the Lorentz and the axial gauges as examples. We show how the Green functions in axial gauge can be written as a series in terms of those in Lorentz gauges. Our method also applies to operator Green's functions. We show that this process involves another set of related FFBRS transfomations that is derivable from infinitesimal FBRS. We suggest possible applications. 
S. D. Joglekar, A. Misra (Department of Physics, Indian Institute of   Technology, Kanpur, UP, India)