⦃G, L1⦄ ⊢ ⬈[h, §l] L2 → ⦃G, L1.ⓑ{I}V1⦄ ⊢ ⬈[h, §l] L2.ⓑ{I}V2.
/2 width=1 by lfxs_gref/ qed.
+lemma lfpx_pair_repl_dx: ∀h,I,G,L1,L2,T,V,V1.
+ ⦃G, L1.ⓑ{I}V⦄ ⊢ ⬈[h, T] L2.ⓑ{I}V1 →
+ ∀V2. ⦃G, L1⦄ ⊢ V ⬈[h] V2 →
+ ⦃G, L1.ⓑ{I}V⦄ ⊢ ⬈[h, T] L2.ⓑ{I}V2.
+/2 width=2 by lfxs_pair_repl_dx/ qed-.
+
(* Basic inversion lemmas ***************************************************)
lemma lfpx_inv_atom_sn: ∀h,I,G,Y2. ⦃G, ⋆⦄ ⊢ ⬈[h, ⓪{I}] Y2 → Y2 = ⋆.