@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/