-lemma crx_append_sn: ∀h,g,G,L,K,T. ⦃G, L⦄ ⊢ 𝐑[h, g]⦃T⦄ → ⦃G, K @@ L⦄ ⊢ 𝐑[h, g]⦃T⦄.
-#h #g #G #L #K0 #T #H elim H -L -T /2 width=1/ /2 width=2/
+lemma crx_append_sn: ∀h,g,G,L,K,T. ⦃G, L⦄ ⊢ ➡[h, g] 𝐑⦃T⦄ → ⦃G, K @@ L⦄ ⊢ ➡[h, g] 𝐑⦃T⦄.
+#h #g #G #L #K0 #T #H elim H -L -T
+/2 width=2 by crx_sort, crx_appl_sn, crx_appl_dx, crx_ri2, crx_ib2_sn, crx_ib2_dx, crx_beta, crx_theta/