1. Abraham, R. and Marsden J.E. 1978:, Foundations of Mechanics, Benjamin/Cummings Publ. Co., Reading, Mass..
2. Birkhoff, G.D. 1927:, Dynamical Systems, Am. Math. Soc, Providence, R.I..
3. Cushman, R., Deprit, A. and Mosak, R. 1983:, Normal forms and representation theory, J. Math. Phy. 24 (8), 2102–2116.
4. Cushman, R., and Sanders, J. 1986:, Nilpotent normal forms and representation theory of s/(2,R), Contemporary Mathematics 56, Amer. Math. Soc, Providence, R.I., 31–51.
5. Deprit, A. 1969:, Canonical transformation depending on a small parameter, Celestial Mechanics 72, 173–79.