1. See, for example, H. Goldstein,Classical Mechanics(Addison-Wesley, Reading, Mass., 1950).
2. The term will be used here in a somewhat broader sense as applying to nonintegrable systems as well. For example, a linear rotor in a collision system might be advantageously treated by the angular momentum variables for the free rotor.
3. Quantum mechanical phase and time operator
4. Phase and Angle Variables in Quantum Mechanics
5. Canonical Transformations and Spectra of Quantum Operators