@article{DE_1987_23_6_a6,
     author = {I. I. Pleshkan},
     title = {On the isochronicity of systems of two differential equations whose right-hand sides contain common factors},
     journal = {Differencialʹnye uravneni\^a},
     pages = {981--993},
     publisher = {mathdoc},
     volume = {23},
     number = {6},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1987_23_6_a6/}
}