Differential systems

This paper deals with aane covariants of autonomous diier-ential systems. We g i v e a constructive method for computing them. This method allows in particular to deduce a (minimal) system of generators of the algebra of aane covariants from one of centro-aaane invariants. In the case of planar quadratic diierential systems, we give a minimal system of the algebra of center-aane covariants and using the previous method we construct a minimal system of generators of the algebra of aane covariants. Computations are made with Maple. All algorithms constitute the package SIB.