@article{RM_1971_26_4_a1,
     author = {M. V. Keldysh},
     title = {On the completeness of the eigenfunctions of some classes of non-selfadjoint linear operators},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {15--44},
     publisher = {mathdoc},
     volume = {26},
     number = {4},
     year = {1971},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_1971_26_4_a1/}
}