We present some results concerning Poincar e-Dulac normal forms of dynamical systems which are symmetric under (possibly nonlinear) Lie point transformations. We show in particular that the vector elds deening the dynamical system and the Lie symmetry can be put into a "joint normal form".

We consider the problem of computing, out of a set C of trees and a rewrite system R, those trees in C that cannot be rewritten into a tree in C. We solve this problem for sets of formulas that are described by dominance graphs, and a certain class of rewrite systems that we use to approximate entailment, and show how to compute the irreducible trees efficiently by intersecting tree automata. O...