@article{DE_1975_11_5_a4,
     author = {A. E. Rudenok},
     title = {Strong isochrony of the center. {Periods} of limit cycles of the {Lienard} system},
     journal = {Differencialʹnye uravneni\^a},
     pages = {811--819},
     publisher = {mathdoc},
     volume = {11},
     number = {5},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_5_a4/}
}