@article{DE_1981_17_5_a23,
     author = {A. A. Samodurov},
     title = {Problem of the center and the integrating factor for a {Li\'enard} equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {936--940},
     year = {1981},
     volume = {17},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1981_17_5_a23/}
}