include "delayed_updating/notation/relations/black_rightarrow_df_3.ma".
include "ground/xoa/ex_4_3.ma".
(* DELAYED FOCUSED REDUCTION ************************************************)
include "delayed_updating/notation/relations/black_rightarrow_df_3.ma".
include "ground/xoa/ex_4_3.ma".
(* DELAYED FOCUSED REDUCTION ************************************************)