(** Reflexive closure is included in the reflexive-transitive closure *)

(* Specifications: *)
Lemma clos_r_clos_rt :
inclusion (clos_refl R) (clos_refl_trans R).
Lemma clos_t_clos_rt :
inclusion (clos_trans R) (clos_refl_trans R).
Lemma clos_rt_t : forall x y z,
clos_refl_trans R x y -> clos_trans R y z ->
clos_trans R x z.