@article{DE_1988_24_4_a25,
     author = {A. S. Pechentsov},
     title = {Basis properties of eigenfunctions of a boundary value problem in the case of a multiple root of the characteristic polynomial},
     journal = {Differencialʹnye uravneni\^a},
     pages = {703--705},
     publisher = {mathdoc},
     volume = {24},
     number = {4},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1988_24_4_a25/}
}