@article{DAN_1975_223_2_a14,
     author = {A. I. Neishtadt},
     title = {Averaging in multifrequency systems},
     journal = {Doklady Akademii Nauk},
     pages = {314--317},
     publisher = {mathdoc},
     volume = {223},
     number = {2},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1975_223_2_a14/}
}