@article{GDZPPN002288923,
title = {On the spectcral theory of elliptic differential operators. I.},
journal = {Mathematische Annalen},
volume = {142},
year = {1961},
pages = {22-130},
url = {http://dml.mathdoc.fr/item/GDZPPN002288923}
}
BROWDER, F.E. On the spectcral theory of elliptic differential operators. I.. Mathematische Annalen, Tome 142 (1961) pp. 22-130. http://gdmltest.u-ga.fr/item/GDZPPN002288923/