@article{IVM_1959_2_a20,
     author = {Yu. A. Ryabov},
     title = {Estimate for the region of convergence of periodic series solutions of differential equations with a~small parameter. {The} case of no resonance},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {202--212},
     publisher = {mathdoc},
     number = {2},
     year = {1959},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1959_2_a20/}
}