@article{DAN_1992_322_6_a3,
     author = {A. D. Bruno},
     title = {Nondegeneracy conditions in the {Kolmogorov} theorem},
     journal = {Doklady Akademii Nauk},
     pages = {1028--1032},
     publisher = {mathdoc},
     volume = {322},
     number = {6},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1992_322_6_a3/}
}