%0 Journal Article
%A José A. Alvarez
%A Teresa Alvarez
%A Manuel González
%T Gap and perturbation of non-semi-Fredholm operators.
%J Extracta Mathematicae
%D 1989
%P 139
%V 4
%N 3
%I mathdoc
%U https://geodesic-test.mathdoc.fr/item/EXMATH_1989__4_3_38327/
%G en
%F EXMATH_1989__4_3_38327