@article{GDZPPN002104474, title = {The ?-constant stratum is not smooth.}, journal = {Inventiones mathematicae}, volume = {88}, year = {1987}, pages = {139-152}, zbl = {0627.32018}, url = {http://dml.mathdoc.fr/item/GDZPPN002104474} }
Luengo, L. The ?-constant stratum is not smooth.. Inventiones mathematicae, Tome 88 (1987) pp. 139-152. http://gdmltest.u-ga.fr/item/GDZPPN002104474/