@article{MZM_1990_47_6_a21,
     author = {V. N. Pyvovarchyk},
     title = {Closedness of the approximate spectrum of a~polynomial operator pencil},
     journal = {Matemati\v{c}eskie zametki},
     pages = {147--148},
     publisher = {mathdoc},
     volume = {47},
     number = {6},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1990_47_6_a21/}
}