@article{DAN_1965_165_5_a1,
     author = {A. D. Bruno},
     title = {On convergence of transforms of differential equations to the normal form},
     journal = {Doklady Akademii Nauk},
     pages = {987--989},
     publisher = {mathdoc},
     volume = {165},
     number = {5},
     year = {1965},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1965_165_5_a1/}
}