@article{DAN_1990_313_2_a2,
     author = {V. I. Zubov},
     title = {Normal form of the phase space of a mechanical system},
     journal = {Doklady Akademii Nauk},
     pages = {273--276},
     publisher = {mathdoc},
     volume = {313},
     number = {2},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_313_2_a2/}
}