1. P. and T. Ehrenfest, The Conceptual Foundations of the Statistical Approach in Mechanics, Cornell University Press, Ithaca, NY, 1959; (translated from Encyclopädie der mathematischen Wisschenchaften, Vol. IV(2), Teubner, Leipzig, 1912).
2. D. ter Haar, Elements of Statistical Mechanics, Rinehart, NY, 1954, p. 100.
3. Classical Mechanics;Goldstein,1980
4. J. Willard Gibbs, Elementary Principles in Statistical mechanics, Yale University Press, 1902. Dover reprint NY.