@article{DE_1989_25_7_a24,
     author = {Z. S. Batalova and N. A. Ezhevskaya},
     title = {The structure of the phase space of the {Duffing} equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1270--1271},
     publisher = {mathdoc},
     volume = {25},
     number = {7},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1989_25_7_a24/}
}