TY  - JOUR
AU  - Breves Filho, J.A.
TI  - On the normal systems of differential equations
JO  - Portugaliae mathematica
PY  - 1974
SP  - 199
EP  - 201
VL  - 33
IS  - 4
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/PORMA_1974__33_4_115239/
LA  - en
ID  - PORMA_1974__33_4_115239
ER  -