TY  - JOUR
AU  - Ian Knowles
TI  - On the Existence of Minimal Operators for Schrödinger-Type Differential Expressions.
JO  - Mathematische Annalen
PY  - 1978
SP  - 221
EP  - 228
VL  - 233
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MAN_1978__233_163109/
ID  - MAN_1978__233_163109
ER  -