@article{DE_1968_4_10_a6,
     author = {Yu. V. Churin},
     title = {The behavior of periodic solutions of a system of second order differential equations with polynomial right-hand sides},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1821--1834},
     publisher = {mathdoc},
     volume = {4},
     number = {10},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1968_4_10_a6/}
}