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Invariant theory in all characteristics, Kingston, Ontario : Canada (2002)
Convex cones and SAGBI bases of permutation invariants
Nicolas M. Thiéry1, Stéphan Thomassé1

Let G be a permutation group acting on {1,...,n}, and < be any admissible term order on the polynomial ring K[x_1,...,x_n]. We prove that the invariant ring K[x_1,...,x_n]^G of G has a finite SAGBI basis if, and only if, G is generated by reflections.
1 :  LAPCS - Laboratoire de Probabilités, Combinatoire et Statistique