%0 Journal Article %A V. I. Gorbaichuk %T An inverse theorem on approximation of functions by operators of extension to a~canonical domain %J Informatics and Automation %D 1987 %P 97-98 %V 180 %I mathdoc %U http://geodesic.mathdoc.fr/item/TRSPY_1987_180_a52/ %G ru %F TRSPY_1987_180_a52