@article{SM_1973_20_3_a1,
     author = {G. V. Radzievskii},
     title = {Multiple completeness of root vectors of {a~Keldysh} pencil perturbed by an operator-valued function analytic in a~disc},
     journal = {Sbornik. Mathematics},
     pages = {323--347},
     publisher = {mathdoc},
     volume = {20},
     number = {3},
     year = {1973},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1973_20_3_a1/}
}