@article{DE_1971_7_9_a22,
     author = {V. S. Mokeichev},
     title = {Periodic boundary value problems and {Riesz} bases},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1714--1720},
     publisher = {mathdoc},
     volume = {7},
     number = {9},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1971_7_9_a22/}
}