(* Second, on domain (exd m): *)

(* Specifications: *)
Lemma surj_A_1:
forall (m:fmap)(k:dim), inv_hmap m ->
surj_dart (exd m) (A_1 m k).
Lemma surj_A:
forall (m:fmap)(k:dim), inv_hmap m ->
surj_dart (exd m) (A m k).