@article{DE_1971_7_2_a17,
     author = {Z. M. Kochetkova},
     title = {The isochrony of a certain system of differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {359--362},
     publisher = {mathdoc},
     volume = {7},
     number = {2},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1971_7_2_a17/}
}