@article{ZVMMF_1986_26_5_a4,
     author = {O. O. Galaktionova and V. A. Zlatoustov},
     title = {$2\pi$-periodic solutions of {Duffing's} equation},
     journal = {\v{Z}urnal vy\v{c}islitelʹnoj matematiki i matemati\v{c}eskoj fiziki},
     pages = {673--685},
     publisher = {mathdoc},
     volume = {26},
     number = {5},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZVMMF_1986_26_5_a4/}
}