TY  - JOUR
AU  - Jöran Friberg
TI  - Partially Hypoelliptic Differential Equations of Finite Type.
JO  - Mathematica Scandinavica
PY  - 1961
SP  - 22
EP  - 42
VL  - 9
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MS2_1961__9_165760/
ID  - MS2_1961__9_165760
ER  -