@article{DE_1970_6_10_a9,
     author = {Yu. K. Metlyaev},
     title = {The periodic solutions of a certain differential equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1824--1830},
     publisher = {mathdoc},
     volume = {6},
     number = {10},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1970_6_10_a9/}
}