%0 Journal Article
%A L. E. Isaev
%T A certain class of operators with spectrum concentrated at zero
%J Doklady Akademii Nauk
%D 1968
%P 783-785
%V 178
%N 4
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1968_178_4_a7/
%G ru
%F DAN_1968_178_4_a7