@article{IM2_1976_10_4_a8,
     author = {G. R. Belitskii},
     title = {Normal forms for formal series and germs of $C^\infty$-mappings with respect to the action of a~group},
     journal = {Izvestiya. Mathematics },
     pages = {809--821},
     publisher = {mathdoc},
     volume = {10},
     number = {4},
     year = {1976},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1976_10_4_a8/}
}