Massless Higher Spin Fields in the AdS Background and BRST Constructions   for Nonlinear Algebras
  The detailed description of the method of the construction of the nilpotent BRST charges for nonlinear algebras of constraints appearing in the description of the massless higher spin fields on the $AdS_D$ background is presented. It is shown that the corresponding BRST charge is not uniquely defined, but this ambiguity has no impact on the physical content of the theory. 
I.L.Buchbinder, A.Pashnev and M. Tsulaia