Lifting a Conformal Field Theory from D-Dimensional Flat Space to   (D+1)-Dimensional Ads Space
  A quantum field theory on Anti-de-Sitter space can be constructed from a conformal field theory on its boundary Minkowski space by an inversion of the holographic mapping. To do this the conformal field theory must satisfy certain constraints. The structure of operator product expansions is carried over to AdS space. We show that this method yields a higher spin field theory HS(4) from the minimal conformal O(N) sigma model in three dimensions. For these models AdS/CFT correspondence is hereby proved to second order in the coupling constant. 
W.Ruehl