TY  - JOUR
AU  - D. Müller
AU  - F. Ricci
TI  - Analysis of second order differential operators on Heisenberg groups. I.
JO  - Inventiones mathematicae
PY  - 1990
SP  - 545
EP  - 582
VL  - 101
IS  - 2
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/IM_1990__101_2_143816/
ID  - IM_1990__101_2_143816
ER  -