1. Cf. any textbook of statistical mechanics,e.g. K. Huang:Statistical Mechanics (New York and London, 1963), p. 150.
2. E. Fermi,J. Pasta andS. Ulam:Los Alamos Sci. Lab. Rep., LA-1940 (1955), reprinted inE. Fermi:Collected Papers (Chicago, 1965), p. 978. See alsoS. Ulam:A Collection of Mathematical Problems (New York, 1960), p. 109.G. Contopoulos:Astron. Journ.,68, 1 (1963);
3. M. Hénon andC. Heiles:Astron. Journ.,69, 73 (1964);
4. P. Bocchieri,A. Scotti,B. Bearzi andA. Loinger:Phys. Rev. A,2, 2013 (1970);
5. F. M. Izrailev,A. I. Khisamutnikov andB. V. Chirikov:Los Alamos Sci. Lab. Rep., LA-440 TR (1970);