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@article{MZM_1990_48_5_a3, author = {A. D. Bruno}, title = {The normal form of a~system, close to {a~Hamiltonian} system}, journal = {Matemati\v{c}eskie zametki}, pages = {35--46}, publisher = {mathdoc}, volume = {48}, number = {5}, year = {1990}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1990_48_5_a3/} }
A. D. Bruno. The normal form of a~system, close to a~Hamiltonian system. Matematičeskie zametki, Tome 48 (1990) no. 5, pp. 35-46. http://geodesic.mathdoc.fr/item/MZM_1990_48_5_a3/