proposition: Theorem ssf_correct': forall e, RegExp.equal e (ssf e).
proof: Proof. intros. apply RegExp.equal_sym, ssf_correct. Qed.
imports: ATBR(Common) ATBR(Classes) ATBR(Graph) ATBR(SemiLattice) ATBR(Monoid) ATBR(SemiRing) ATBR(KleeneAlgebra) ATBR(Model_RegExp) Coq(Bool)