(** ** TM to SRH' *)

(** ** SRH' to SRH *)
Lemma rewt_R_fresh (R : SRS) (x : string) (A l : list symbol) :
rewt (R ++ map (fun a : symbol => [a] / [fresh (sym R ++ x)]) A) x l -> ~ fresh (sym R ++ x) el l -> rewt R x l.