@article{1077467073,
author = {Hartman, Philip and Putnam, Calvin R.},
title = {The essential spectra belonging to bounded and half-bounded
potentials},
journal = {Duke Math. J.},
volume = {23},
number = {1},
year = {1956},
pages = { 561-570},
language = {en},
url = {http://dml.mathdoc.fr/item/1077467073}
}
Hartman, Philip; Putnam, Calvin R. The essential spectra belonging to bounded and half-bounded
potentials. Duke Math. J., Tome 23 (1956) no. 1, pp. 561-570. http://gdmltest.u-ga.fr/item/1077467073/