@article{DE_2000_36_4_a18,
     author = {A. A. Grin'},
     title = {A cubic {Dulac} function for a polynomial autonomous system on the plane with right-hand sides that are fourth-order nonlinearities},
     journal = {Differencialʹnye uravneni\^a},
     pages = {558--560},
     year = {2000},
     volume = {36},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_2000_36_4_a18/}
}