(* pre_ring0_Br1 is defined *)
(*============================================================ NEW double_link_list PROPERTIES: OK! =============================================================*)
(* OK! *)

Lemma expe_expe_B0: forall(m:fmap)(x z t:dart),
inv_hmap m -> exd m x ->
let m0 := B m zero x in
~ expe m x z ->
expe m z t-> expe m0 z t.