@article{MAN_1961__142_160823,
     author = {F.E. BROWDER},
     title = {On the spectcral theory of elliptic differential operators. {I.}},
     journal = {Mathematische Annalen},
     pages = {22--130},
     year = {1961},
     volume = {142},
     url = {http://geodesic.mathdoc.fr/item/MAN_1961__142_160823/}
}