@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/