@article{DE_1974_10_4_a9,
     author = {I. I. Pleshkan},
     title = {On the problem of isochronism for systems with discontinuous right-hand sides},
     journal = {Differencialʹnye uravneni\^a},
     pages = {647--658},
     publisher = {mathdoc},
     volume = {10},
     number = {4},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1974_10_4_a9/}
}