@article{RM_1969_24_5_a12,
     author = {N. N. Nekhoroshev},
     title = {Two theorems on the action-angle variables},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     publisher = {mathdoc},
     volume = {24},
     number = {5},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1969_24_5_a12/}
}