Remarks on quantization of Pais-Uhlenbeck oscillators
  This work is concerned with a quantization of the Pais-Uhlenbeck oscillators from the point of view of their multi-Hamiltonian structures. It is shown that the 2n-th order oscillator with a simple spectrum is equivalent to the usual anisotropic n - dimensional oscillator. 
E.V. Damaskinsky and M.A. Sokolov