@article{DE_1977_13_5_a11,
     author = {S. P. Tokarev},
     title = {Smooth equivalence of systems of differential equations on the plane in the case of a structurally unstable focus},
     journal = {Differencialʹnye uravneni\^a},
     pages = {892--897},
     year = {1977},
     volume = {13},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_5_a11/}
}