@article{DE_1997_33_10_a19,
     author = {L. A. Cherkas and A. A. Grin'},
     title = {A second-degree polynomial {Dulac} function for a cubic system on the plane},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1435--1436},
     publisher = {mathdoc},
     volume = {33},
     number = {10},
     year = {1997},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1997_33_10_a19/}
}