@article{DE_2006_42_6_a0,
     author = {A. I. Vagabov and Z. A. Abdurakhmanov},
     title = {Conditions for the $k$-fold completeness ($0<k\le n$) of root functions of an $n$th-order ordinary differential operator pencil},
     journal = {Differencialʹnye uravneni\^a},
     pages = {723--730},
     publisher = {mathdoc},
     volume = {42},
     number = {6},
     year = {2006},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_2006_42_6_a0/}
}