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								[1]
								. Goldstein H. Classical Mechanics, 2nd ed. Massachusetts: Addison-Wesley, 1980. 378—418 2. Dragt A J, Finn J M. Lie Series and Invariant Functions for Analytic Symplectic Maps. J Math Phys., 1976, 17(12): 2215 
. Goldstein H. Classical Mechanics, 2nd ed. Massachusetts: Addison-Wesley, 1980. 378—418 2. Dragt A J, Finn J M. Lie Series and Invariant Functions for Analytic Symplectic Maps. J Math Phys., 1976, 17(12): 2215