%0 Journal Article
%A S. G. Krein
%A V. I. Fomin
%T Small perturbations of singular differential equations with
%J Doklady Akademii Nauk
%D 1990
%P 77-79
%V 314
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1990_314_1_a18/
%G ru
%F DAN_1990_314_1_a18