1. H. Poincaré:Les méthodes nouvelles de la mécanique celeste, Vol. 1 (Paris, 1892), Chapt. 5. See alsoE. T. Whittaker:A Treatise on the Analytical Dynamics of Particles and Rigid Bodies (New York, 1944), par. 165.
2. E. Fermi:Nouvo Cimento,26, 105 (1923).
3. E. Fermi:Nuovo Cimento,25, 267 (1923);Phys. Z.,24, 261 (1923).
4. W. Urbanski:Phys. Z.,25, 47 (1924);E. Fermi:Phys. Z.,25, 166 (1924).
5. A. N. Kolmogorov:Dokl. Akad. Nauk SSSR,98, 527 (1954); translated inLecture Notes in Physics,93, edited byG. Casati andJ. Ford (Berlin, 1979);V. I. Arnold:Russ. Math. Surv.,18, 9 (1963);18, 85 (1963);J. K. Moser:Nachr. Akad. Wiss. Gottingen, Math-Phys. Kl., 1 (1962).