%0 Journal Article
%A W. Hansen
%A Z. Ma
%T Perturbation by differences of unbounded potentials.
%J Mathematische Annalen
%D 1990
%P 553-570
%V 287
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/MAN_1990__287_1_164705/
%F MAN_1990__287_1_164705