-(* Note: missing in basic_2A1 *)
-lemma lfdeq_inv_lifts_bi: ∀h,o,L1,L2,U. L1 ≡[h, o, U] L2 →
- ∀K1,K2,i. ⬇*[i] L1 ≡ K1 → ⬇*[i] L2 ≡ K2 →
- ∀T. ⬆*[i] T ≡ U → K1 ≡[h, o, T] K2.
-/2 width=8 by lfxs_inv_lifts_bi/ qed-.
+(* Basic_2A1: uses: lleq_inv_lift_le lleq_inv_lift_be lleq_inv_lift_ge *)
+lemma lfdeq_inv_lifts_bi: ∀h,o,L1,L2,U. L1 ≡[h, o, U] L2 → ∀b,f. 𝐔⦃f⦄ →
+ ∀K1,K2. ⬇*[b, f] L1 ≡ K1 → ⬇*[b, f] L2 ≡ K2 →
+ ∀T. ⬆*[f] T ≡ U → K1 ≡[h, o, T] K2.
+/2 width=10 by lfxs_inv_lifts_bi/ qed-.