@article{DE_1982_18_5_a14,
     author = {L. A. Cherkas},
     title = {On the question of the analyticity of a manifold that defines limit cycles},
     journal = {Differencialʹnye uravneni\^a},
     pages = {839--845},
     publisher = {mathdoc},
     volume = {18},
     number = {5},
     year = {1982},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1982_18_5_a14/}
}