@article{DE_1981_17_3_a4,
     author = {L. A. Cherkas},
     title = {Structure of the sequence function in the neighborhood of a separatrix cycle during perturbation of an analytic autonomous system on the plane},
     journal = {Differencialʹnye uravneni\^a},
     pages = {469--478},
     publisher = {mathdoc},
     volume = {17},
     number = {3},
     year = {1981},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1981_17_3_a4/}
}