@article{SM_1992_73_2_a8,
     author = {E. R. Avakov and A. A. Agrachev and A. V. Arutyunov},
     title = {The level set of a~smooth mapping in a~neighborhood of a~singular point, and zeros of a~quadratic mapping},
     journal = {Sbornik. Mathematics},
     pages = {455--466},
     publisher = {mathdoc},
     volume = {73},
     number = {2},
     year = {1992},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1992_73_2_a8/}
}