@article{GDZPPN002419211, title = {Upper and Lower Fredholm Spectra II.}, journal = {Mathematische Zeitschrift}, volume = {154}, year = {1977}, pages = {253-256}, zbl = {0393.47001}, url = {http://dml.mathdoc.fr/item/GDZPPN002419211} }
Harte, Robin; Anthony, Wickstead. Upper and Lower Fredholm Spectra II.. Mathematische Zeitschrift, Tome 154 (1977) pp. 253-256. http://gdmltest.u-ga.fr/item/GDZPPN002419211/