namespace boost {
  namespace numeric {
    namespace odeint {
      template<typename Stepper, 
               typename StepperCategory = typename Stepper::stepper_category> 
        class dense_output_runge_kutta;

      template<typename Stepper> 
        class dense_output_runge_kutta<Stepper, stepper_tag>;
      template<typename Stepper> 
        class dense_output_runge_kutta<Stepper, explicit_controlled_stepper_fsal_tag>;
    }
  }
}