@article{IVM_1988_11_a7,
     author = {G. I. Russu},
     title = {The spectrum of an operator in a~couple of {Banach} spaces},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {42--49},
     year = {1988},
     number = {11},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1988_11_a7/}
}