Hypersurfaces of constant higher order mean curvature in warped products
  In this paper we characterize compact and complete hypersurfaces with some constant higher order mean curvature into warped product spaces. Our approach is based on the use of a new trace operator version of the Omori-Yau maximum principle which seems to be interesting in its own. 
Luis J. Alias, Debora Impera and Marco Rigoli
math.DG