@article{DE_1992_28_7_a2,
     author = {A. P. Sadovskii},
     title = {Focal values of a cubic system of nonlinear oscillations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1122--1127},
     publisher = {mathdoc},
     volume = {28},
     number = {7},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1992_28_7_a2/}
}