@article{DAN_1974_216_2_a2,
     author = {A. D. Bruno},
     title = {Analytic integral manifolds},
     journal = {Doklady Akademii Nauk},
     pages = {253--256},
     year = {1974},
     volume = {216},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1974_216_2_a2/}
}