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@article{DAN_1968_178_4_a7, author = {L. E. Isaev}, title = {A certain class of operators with spectrum concentrated at zero}, journal = {Doklady Akademii Nauk}, pages = {783--785}, publisher = {mathdoc}, volume = {178}, number = {4}, year = {1968}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1968_178_4_a7/} }
L. E. Isaev. A certain class of operators with spectrum concentrated at zero. Doklady Akademii Nauk, Tome 178 (1968) no. 4, pp. 783-785. http://geodesic.mathdoc.fr/item/DAN_1968_178_4_a7/