@article{DAN_1982_264_1_a8,
     author = {Yu. A. Konyaev},
     title = {On the existence of periodic solutions of some systems of differential equations with a small parameter at the derivative},
     journal = {Doklady Akademii Nauk},
     pages = {40--44},
     publisher = {mathdoc},
     volume = {264},
     number = {1},
     year = {1982},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1982_264_1_a8/}
}