intros Q p q H'; inversion H'; auto.
Qed.
Hint Resolve reducestar_reduceplus.

Theorem reducestar_inv :
forall (Q : list (poly A0 eqA ltM)) (p q : list (Term A n)),
reducestar Q p q ->
canonical A0 eqA ltM p ->
eqP A eqA n p q /\
irreducible A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec Q p \/
(exists r : list (Term A n),
reduce A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec Q p r /\
reducestar Q r q).