@article{DE_1988_24_4_a16,
     author = {N. N. Dedok},
     title = {Limit cycles of a system of differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {683--684},
     publisher = {mathdoc},
     volume = {24},
     number = {4},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1988_24_4_a16/}
}