\Omb \rightarrow \Omc , \Omc ^* $ transitions: Model-independent bounds   on invariant form factors
  In this note we report some model-independent bounds involving transition form factors for $ \Omb \rightarrow \Omc $ and $ \Omb \rightarrow \Omc ^* $ and the nonperturbative matrix elements of the $ \Omb $ system. They are derived by using operator product expansion (OPE) in Heavy Quark Effective Theory . 
J.G.K\"orner, K.Melnikov, O.Yakovlev