%0 Journal Article
%A A. S. Markus
%T The root-vector expansion of a weakly perturbed self-adjoint operator
%J Doklady Akademii Nauk
%D 1962
%P 538-541
%V 142
%N 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1962_142_3_a9/
%G ru
%F DAN_1962_142_3_a9