%0 Journal Article
%A V. A. Il'in
%T An estimate for the difference of the Riesz means of two spectral expansions for a function in the class~$L_2$
%J Differencialʹnye uravneniâ
%D 1988
%P 852-863
%V 24
%N 5
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1988_24_5_a14/
%G ru
%F DE_1988_24_5_a14