Existence of Invariant Tori for Differentiable Hamiltonian Vector Fields   without Action-Angle Variables
  We proved the existence of invariant tori in differentiable Hamiltonian vector fields without action-angle variables. It is a generalization of the result of [Llave, 2005] that deals with analytic vector fields. 
Wu-Hwan Jong and Jin-Chol Paek
math-ph math.DS math.MP