@article{1077379127, author = {Nussbaum, Roger D.}, title = {The radius of the essential spectrum}, journal = {Duke Math. J.}, volume = {37}, number = {1}, year = {1970}, pages = { 473-478}, language = {en}, url = {http://dml.mathdoc.fr/item/1077379127} }
Nussbaum, Roger D. The radius of the essential spectrum. Duke Math. J., Tome 37 (1970) no. 1, pp. 473-478. http://gdmltest.u-ga.fr/item/1077379127/