@article{DE_1984_20_5_a28,
     author = {N. P. Morozov},
     title = {On periodic solutions of a system of equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {904--905},
     publisher = {mathdoc},
     volume = {20},
     number = {5},
     year = {1984},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1984_20_5_a28/}
}