@article{MZM_1983_33_3_a1,
     author = {A. D. Bryuno},
     title = {Noncanonical invariants of {Hamiltonian} systems},
     journal = {Matemati\v{c}eskie zametki},
     pages = {333--344},
     publisher = {mathdoc},
     volume = {33},
     number = {3},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1983_33_3_a1/}
}