@article{DE_1973_9_7_a12,
     author = {V. F. Filiptsov},
     title = {Algebraic limit cycles},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1281--1288},
     year = {1973},
     volume = {9},
     number = {7},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_7_a12/}
}