+lemma nta_inv_ldef_sn (a) (h) (G) (K) (V):
+ ∀X2. ⦃G,K.ⓓV⦄ ⊢ #0 :[a,h] X2 →
+ ∃∃W,U. ⦃G,K⦄ ⊢ V :[a,h] W & ⬆*[1] W ≘ U & ⦃G,K.ⓓV⦄ ⊢ U ⬌*[h] X2 & ⦃G,K.ⓓV⦄ ⊢ X2 ![a,h].
+#a #h #G #Y #X #X2 #H
+elim (cnv_inv_cast … H) -H #X1 #HX2 #H1 #HX21 #H2
+elim (cnv_inv_zero … H1) -H1 #Z #K #V #HV #H destruct
+elim (cpms_inv_delta_sn … H2) -H2 *
+[ #_ #H destruct
+| #W #HVW #HWX1
+ /3 width=5 by cnv_cpms_nta, cpcs_cprs_sn, ex4_2_intro/
+]
+qed-.
+
+lemma nta_inv_lref_sn (a) (h) (G) (L):
+ ∀X2,i. ⦃G,L⦄ ⊢ #↑i :[a,h] X2 →
+ ∃∃I,K,T2,U2. ⦃G,K⦄ ⊢ #i :[a,h] T2 & ⬆*[1] T2 ≘ U2 & ⦃G,K.ⓘ{I}⦄ ⊢ U2 ⬌*[h] X2 & ⦃G,K.ⓘ{I}⦄ ⊢ X2 ![a,h] & L = K.ⓘ{I}.
+#a #h #G #L #X2 #i #H
+elim (cnv_inv_cast … H) -H #X1 #HX2 #H1 #HX21 #H2
+elim (cnv_inv_lref … H1) -H1 #I #K #Hi #H destruct
+elim (cpms_inv_lref_sn … H2) -H2 *
+[ #_ #H destruct
+| #X #HX #HX1
+ /3 width=9 by cnv_cpms_nta, cpcs_cprs_sn, ex5_4_intro/
+]
+qed-.
+
+lemma nta_inv_lref_sn_drops_cnv (a) (h) (G) (L):
+ ∀X2, i. ⦃G,L⦄ ⊢ #i :[a,h] X2 →
+ ∨∨ ∃∃K,V,W,U. ⬇*[i] L ≘ K.ⓓV & ⦃G,K⦄ ⊢ V :[a,h] W & ⬆*[↑i] W ≘ U & ⦃G,L⦄ ⊢ U ⬌*[h] X2 & ⦃G,L⦄ ⊢ X2 ![a,h]
+ | ∃∃K,W,U. ⬇*[i] L ≘ K. ⓛW & ⦃G,K⦄ ⊢ W ![a,h] & ⬆*[↑i] W ≘ U & ⦃G,L⦄ ⊢ U ⬌*[h] X2 & ⦃G,L⦄ ⊢ X2 ![a,h].
+#a #h #G #L #X2 #i #H
+elim (cnv_inv_cast … H) -H #X1 #HX2 #H1 #HX21 #H2
+elim (cnv_inv_lref_drops … H1) -H1 #I #K #V #HLK #HV
+elim (cpms_inv_lref1_drops … H2) -H2 *
+[ #_ #H destruct
+| #Y #X #W #H #HVW #HUX1
+ lapply (drops_mono … H … HLK) -H #H destruct
+ /4 width=8 by cnv_cpms_nta, cpcs_cprs_sn, ex5_4_intro, or_introl/
+| #n #Y #X #U #H #HVU #HUX1 #H0 destruct
+ lapply (drops_mono … H … HLK) -H #H destruct
+ elim (lifts_total V (𝐔❴↑i❵)) #W #HVW
+ lapply (cpms_lifts_bi … HVU (Ⓣ) … L … HVW … HUX1) -U
+ [ /2 width=2 by drops_isuni_fwd_drop2/ ] #HWX1
+ /4 width=9 by cprs_div, ex5_3_intro, or_intror/
+]
+qed-.
+