@article{1077476396, author = {Newburgh, J. D.}, title = {The variation of spectra}, journal = {Duke Math. J.}, volume = {18}, number = {1}, year = {1951}, pages = { 165-176}, language = {en}, url = {http://dml.mathdoc.fr/item/1077476396} }
Newburgh, J. D. The variation of spectra. Duke Math. J., Tome 18 (1951) no. 1, pp. 165-176. http://gdmltest.u-ga.fr/item/1077476396/