- L ⊢ U1 [d, e] ≫* U2 → ∀T1. ↑[d, e] T1 ≡ U1 → U1 = U2.
-#L #U1 #U2 #d #e #H #T1 #HTU1 @(tpss_ind … H) -H U2 //
-#U #U2 #_ #HU2 #IHU destruct -U1
-<(tps_inv_lift1_eq … HU2 … HTU1) -HU2 HTU1 //
+ L ⊢ U1 [d, e] ≫* U2 → ∀T1. ⇑[d, e] T1 ≡ U1 → U1 = U2.
+#L #U1 #U2 #d #e #H #T1 #HTU1 @(tpss_ind … H) -U2 //
+#U #U2 #_ #HU2 #IHU destruct
+<(tps_inv_lift1_eq … HU2 … HTU1) -HU2 -HTU1 //
+qed.
+
+lemma tpss_inv_lift1_be_up: ∀L,U1,U2,dt,et. L ⊢ U1 [dt, et] ≫* U2 →
+ ∀K,d,e. ⇓[d, e] L ≡ K → ∀T1. ⇑[d, e] T1 ≡ U1 →
+ dt ≤ d → dt + et ≤ d + e →
+ ∃∃T2. K ⊢ T1 [dt, d - dt] ≫* T2 & ⇑[d, e] T2 ≡ U2.
+#L #U1 #U2 #dt #et #H #K #d #e #HLK #T1 #HTU1 #Hdtd #Hdetde @(tpss_ind … H) -U2
+[ /2 width=3/
+| -HTU1 #U #U2 #_ #HU2 * #T #HT1 #HTU
+ elim (tps_inv_lift1_be_up … HU2 … HLK … HTU ? ?) -HU2 -HLK -HTU // /3 width=3/
+]