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@article{IVM_1989_1_a5, author = {G. G. Islamov}, title = {Extremal perturbations of closed operators}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {35--41}, publisher = {mathdoc}, number = {1}, year = {1989}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1989_1_a5/} }
G. G. Islamov. Extremal perturbations of closed operators. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 1 (1989), pp. 35-41. http://geodesic.mathdoc.fr/item/IVM_1989_1_a5/