@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/}
}