TY  - JOUR
AU  - Lars Hörmander
TI  - A Class of Hypoelliptic Pseudodifferential Operators with Double Characteristics.
JO  - Mathematische Annalen
PY  - 1975
SP  - 165
EP  - 188
VL  - 217
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MAN_1975__217_162768/
ID  - MAN_1975__217_162768
ER  -