@article{DE_1999_35_1_a7,
     author = {L. V. Detchenya and A. P. Sadovskii},
     title = {Orbital normal forms of two-dimensional analytic systems with zero linear and nonzero quadratic parts},
     journal = {Differencialʹnye uravneni\^a},
     pages = {51--57},
     publisher = {mathdoc},
     volume = {35},
     number = {1},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1999_35_1_a7/}
}