@article{DE_1977_13_6_a24,
     author = {S. P. Tokarev},
     title = {The normal form of an analytic system of differential equations in the case of a structurally unstable focus},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1142--1144},
     publisher = {mathdoc},
     volume = {13},
     number = {6},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_6_a24/}
}