1. Analytical Dynamics;Whittaker,1978
2. A third integral of motion in a Galaxy;Contopoulos;Z. Astrophys.,1960
3. An application of the third integral in the velocity space;Barbaris;Z. Astrophys.,1963
4. On the existence of a third integral of motion;Contopoulos;Astron. J.,1963
5. Non-linear coupling of two harmonic oscillations;Hori;Publ. A. S. Japan,1967