TY  - JOUR
AU  - Z. Kowalski
TI  - Generalized characteristic directions for a system of differential equations
JO  - Annales Polonici Mathematici
PY  - 1959
SP  - 269
EP  - 280
VL  - 6
IS  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/articles/10.4064/ap-6-3-269-280/
DO  - 10.4064/ap-6-3-269-280
LA  - en
ID  - 10_4064_ap_6_3_269_280
ER  -