@article{DAN_1967_172_5_a2,
     author = {E. D. Garber},
     title = {Periodic solutions of certain non-linear differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {1003--1006},
     publisher = {mathdoc},
     volume = {172},
     number = {5},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1967_172_5_a2/}
}