Galilean equations for massless fields
  Galilei-invariant equations for massless fields are obtained via contractions of relativistic wave equations. It is shown that the collection of non-equivalent Galilei-invariant wave equations for massless fields with spin equal 1 and 0 is very reach and corresponds to various contractions of the representations of the Lorentz group to those of the Galilei one. It describes many physically consistent systems, e.g., those of electromagnetic fields in various media or Galilean Chern-Simon models. Finally, classification of all linear and a big group of non-linear Galilei-invariant equations for massless fields is presented. 
J.Niederle and A.G. Nikitin