@article{DE_1969_5_3_a4,
     author = {B. M. Arkhipov},
     title = {A nonlinear periodic boundary value problem for an equation and a system of equations of the second order},
     journal = {Differencialʹnye uravneni\^a},
     pages = {456--462},
     publisher = {mathdoc},
     volume = {5},
     number = {3},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1969_5_3_a4/}
}