@article{IVM_1980_1_a15,
     author = {Din' Bat Tkham and N. Ya. Krupnik},
     title = {Perturbation of linear operators},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {74--75},
     publisher = {mathdoc},
     number = {1},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1980_1_a15/}
}