@article{GDZPPN002315548,
title = {On the Existence of Minimal Operators for Schr\"odinger-Type Differential Expressions.},
journal = {Mathematische Annalen},
volume = {237},
year = {1978},
pages = {221-228},
zbl = {0376.35016},
url = {http://dml.mathdoc.fr/item/GDZPPN002315548}
}
Knowles, Ian. On the Existence of Minimal Operators for Schrödinger-Type Differential Expressions.. Mathematische Annalen, Tome 237 (1978) pp. 221-228. http://gdmltest.u-ga.fr/item/GDZPPN002315548/