@article{1250129196,
author = {Protter, M.H.},
title = {The generalized spectrum of second order elliptic systems},
journal = {Rocky Mountain J. Math.},
volume = {9},
number = {4},
year = {1979},
pages = { 503-518},
language = {en},
url = {http://dml.mathdoc.fr/item/1250129196}
}
Protter, M.H. The generalized spectrum of second order elliptic systems. Rocky Mountain J. Math., Tome 9 (1979) no. 4, pp. 503-518. http://gdmltest.u-ga.fr/item/1250129196/