@article{DAN_1986_286_4_a6,
     author = {N. B. Kerimov},
     title = {Unconditional basis property of a system of eigen- and associated},
     journal = {Doklady Akademii Nauk},
     pages = {803--808},
     year = {1986},
     volume = {286},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1986_286_4_a6/}
}