@article{bwmeta1.element.bwnjournal-article-apmv6i3p269bwm,
author = {Kowalski, Z.},
title = {Generalized characteristic directions for a system of differential equations},
journal = {Annales Polonici Mathematici},
volume = {7},
year = {1959},
pages = {269-280},
zbl = {0107.06905},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-apmv6i3p269bwm}
}
Kowalski, Z. Generalized characteristic directions for a system of differential equations. Annales Polonici Mathematici, Tome 7 (1959) pp. 269-280. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-apmv6i3p269bwm/