@article{GDZPPN002345048,
title = {Estimates of the Friedrichs-Lewy type for mixed problems in the theory of linear hyperbolic differential equations in two independent variables},
journal = {Mathematica Scandinavica},
volume = {5},
year = {1957},
pages = {93-114},
zbl = {0078.08601},
url = {http://dml.mathdoc.fr/item/GDZPPN002345048}
}
THOMÉE, VIDAR. Estimates of the Friedrichs-Lewy type for mixed problems in the theory of linear hyperbolic differential equations in two independent variables. Mathematica Scandinavica, Tome 5 (1957) pp. 93-114. http://gdmltest.u-ga.fr/item/GDZPPN002345048/