@article{FAA_1977_11_1_a6,
     author = {R. I. Bogdanov},
     title = {Modules of $C^\infty$-orbital normal forms for singular points of vector fields on a plane},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {57--58},
     publisher = {mathdoc},
     volume = {11},
     number = {1},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_1977_11_1_a6/}
}