A New Approach to Adaptive Nonlinear Regulation
  This paper shows how the theory of adaptive observers can be effectively used in the design internal models for nonlinear output regulation. The main result obtained in this way is a new method for the synthesis of adaptive internal models which substantially enhances the existing theory of adaptive output regulation, by allowing nonlinear internal models and more general classes of controlled plants. 
Francesco Delli Priscoli, Lorenzo Marconi, Alberto Isidori