@article{DAN_1983_273_4_a1,
     author = {A. D. Bruno},
     title = {Analytic invariants of a differential equation},
     journal = {Doklady Akademii Nauk},
     pages = {781--785},
     publisher = {mathdoc},
     volume = {273},
     number = {4},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1983_273_4_a1/}
}