@article{DE_1993_29_1_a3,
     author = {V. D. Budaev},
     title = {A necessary condition for the {Riesz} basis property of systems of root functions of an ordinary nonselfadjoint differential operator},
     journal = {Differencialʹnye uravneni\^a},
     pages = {20--29},
     publisher = {mathdoc},
     volume = {29},
     number = {1},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1993_29_1_a3/}
}