@article{DAN_1958_118_4_a4,
     author = {Yu. A. Ryabov},
     title = {Estimations of the convergence region of periodical series representing solutions of differential equations involving a small parameter},
     journal = {Doklady Akademii Nauk},
     pages = {642--645},
     publisher = {mathdoc},
     volume = {118},
     number = {4},
     year = {1958},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1958_118_4_a4/}
}