Extracting Multidimensional Phase Space Topology from Periodic Orbits
  We establish a hierarchical ordering of periodic orbits in a strongly coupled multidimensional Hamiltonian system. Phase space structures can be reconstructed quantitatively from the knowledge of periodic orbits alone. We illustrate our findings for the hydrogen atom in crossed electric and magnetic fields. 
S. Gekle, J. Main, T. Bartsch, T. Uzer