1. W. R. Davis andM. K. Moss:Nuovo Cimento,27, 1492 (1963).
2. W. R. Davis andM. K. Moss:Nuovo Cimento,38, 1531 (1965).
3. W. R. Davis and.G. H. Katzin:Amer. Journ. Phys.,30, 750 (1962).
4. L. P. Eisenhart: RiemannianGeometry (Princeton, N. J., 1926), p. 128.
5. For a brief discussion of certain mechanical systems possessing quadratic integrals other than the energy integral seeE. T. Whittaker:A Treatise on the Analytical Dynamics of Particles and Rigid Bodies, 4th Ed. (New York, 1944),p. 335.