Classification of surface charges for a spin 2 field on a curved   background solution
  We give an explicit proof of the result that non trivial conserved n-2 forms for a spin 2 field on a background corresponding to a solution to Einstein's equation (with or without cosmological constant) are characterized uniquely by the Killing vector fields of the background. 
Glenn Barnich, Serge Leclercq and Philippe Spindel