%0 Journal Article %A V. I. Burenkov %T On the additivity of the classes of $W_p^{(r)}(\Omega )$ %J Informatics and Automation %D 1967 %P 31-55 %V 89 %I mathdoc %U http://geodesic.mathdoc.fr/item/TRSPY_1967_89_a3/ %G ru %F TRSPY_1967_89_a3