@article{DE_1975_11_11_a23,
     author = {A. P. Sadovskii},
     title = {Solution of the problem of the center and focus for a {Li\'enard} system with polynomial coefficients},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2102--2104},
     publisher = {mathdoc},
     volume = {11},
     number = {11},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_11_a23/}
}