@article{DE_1998_34_3_a2,
     author = {Yu. F. Kalin and N. I. Vulpe},
     title = {Affine-invariant conditions for the topological discrimination of quadratic {Hamiltonian} differential systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {298--302},
     publisher = {mathdoc},
     volume = {34},
     number = {3},
     year = {1998},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1998_34_3_a2/}
}