@article{DE_1974_10_3_a18,
     author = {I. A. Konovalov},
     title = {The limit cycles of a certain dynamical system},
     journal = {Differencialʹnye uravneni\^a},
     pages = {547--549},
     publisher = {mathdoc},
     volume = {10},
     number = {3},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1974_10_3_a18/}
}