TY  - JOUR
AU  - L Luengo
TI  - The ?-constant stratum is not smooth.
JO  - Inventiones mathematicae
PY  - 1987
SP  - 139
EP  - 152
VL  - 90
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/IM_1987__90_143503/
ID  - IM_1987__90_143503
ER  -