Vol. 68,   2   (1999) pp.   243-247
EXISTENCE OF CONSERVATION LAWS IN NILPOTENT CASE
M. MEHDI
Abstract. 
Using the Spencer-Goldschmidt version of the Cartan-Kahler theorem, we prove the local existence of conservation laws for analytical quasi-linear systems of two independent variables in the nilpotent and $2$-cyclic case.