@article{DE_1965_1_3_a7,
     author = {A. Ya. Khokhryakov and B. M. Arkhipov},
     title = {A theorem on a differential inequality for a periodic boundary value problem for an ordinary differential equation of the second order},
     journal = {Differencialʹnye uravneni\^a},
     pages = {335--345},
     publisher = {mathdoc},
     volume = {1},
     number = {3},
     year = {1965},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1965_1_3_a7/}
}