@article{GDZPPN002329492,
title = {Nonstrictly Hyperbolic Nonlinear Systems.},
journal = {Mathematische Annalen},
volume = {277},
year = {1987},
pages = {213-232},
zbl = {0614.35060},
url = {http://dml.mathdoc.fr/item/GDZPPN002329492}
}
Craig, Walter. Nonstrictly Hyperbolic Nonlinear Systems.. Mathematische Annalen, Tome 277 (1987) pp. 213-232. http://gdmltest.u-ga.fr/item/GDZPPN002329492/