@article{IVM_1995_11_a3,
     author = {V. V. Arestov and V. N. Gabushin},
     title = {Best approximation of unbounded operators by bounded operators},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {42--68},
     year = {1995},
     number = {11},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1995_11_a3/}
}