TY  - JOUR
AU  - E. I. Ganzha
TI  - Hypoellipticity of a second-order differential operator with quadratic form of variable sign
JO  - Trudy Matematicheskogo Instituta imeni V.A. Steklova
PY  - 1986
SP  - 175
EP  - 176
VL  - 41
IS  - 4
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/RM_1986_41_4_a5/
LA  - en
ID  - RM_1986_41_4_a5
ER  -