Instance Permutation_refl' : Proper (Logic.eq ==> Permutation) id.

(* Specifications: *)
Theorem Permutation_sym : forall l l' : list A, Permutation l l' -> Permutation l' l.
Theorem Permutation_trans : forall l l' l'' : list A, Permutation l l' -> Permutation l' l'' -> Permutation l l''.