%0 Journal Article
%A L Luengo
%T The ?-constant stratum is not smooth.
%J Inventiones mathematicae
%D 1987
%P 139-152
%V 90
%I mathdoc
%U http://geodesic.mathdoc.fr/item/IM_1987__90_143503/
%F IM_1987__90_143503