-(* Basic forward lemmas *****************************************************)
-
-lemma lfsx_fwd_bind_sn: ∀h,o,a,I,G,L,V,T,l. G ⊢ ⬈*[h, o, ⓑ{a,I}V.T, l] L →
- G ⊢ ⬈*[h, o, V, l] L.
-#h #o #a #I #G #L #V #T #l #H @(lfsx_ind … H) -L
-#L1 #_ #IHL1 @lfsx_intro
-#L2 #HL12 #HV @IHL1 /3 width=4 by lfdeq_fwd_bind_sn/
-qed-.
-
-lemma lfsx_fwd_flat_sn: ∀h,o,I,G,L,V,T,l. G ⊢ ⬈*[h, o, ⓕ{I}V.T, l] L →
- G ⊢ ⬈*[h, o, V, l] L.
-#h #o #I #G #L #V #T #l #H @(lfsx_ind … H) -L
-#L1 #_ #IHL1 @lfsx_intro
-#L2 #HL12 #HV @IHL1 /3 width=3 by lfdeq_fwd_flat_sn/
-qed-.
+lemma lfsx_unit: ∀h,o,I,G,L. G ⊢ ⬈*[h, o, #0] 𝐒⦃L.ⓤ{I}⦄.
+#h #o #I #G #L1 @lfsx_intro
+#Y #HY #HnY elim HnY -HnY /2 width=2 by lfxs_unit_sn/
+qed.