@article{MZM_1973_14_4_a5,
     author = {A. D. Bruno},
     title = {Local invariants of differential equations},
     journal = {Matemati\v{c}eskie zametki},
     pages = {499--507},
     publisher = {mathdoc},
     volume = {14},
     number = {4},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1973_14_4_a5/}
}