-lemma leq_inv_zero2: ∀I2,K2,L1,V2. L1 ≃[0, 0] K2.ⓑ{I2}V2 →
- ∃∃I1,K1,V1. K1 ≃[0, 0] K2 & L1 = K1.ⓑ{I1}V1.
+lemma leq_inv_succ: ∀I1,I2,L1,L2,V1,V2,d,e. L1.ⓑ{I1}V1 ⩬[d, e] L2.ⓑ{I2}V2 → 0 < d →
+ L1 ⩬[⫰d, e] L2.
+#I1 #I2 #L1 #L2 #V1 #V2 #d #e #H #Hd elim (leq_inv_succ1 … H) -H //
+#Z #Y #X #HL12 #H destruct //
+qed-.
+
+lemma leq_inv_zero2: ∀I2,K2,L1,V2. L1 ⩬[0, 0] K2.ⓑ{I2}V2 →
+ ∃∃I1,K1,V1. K1 ⩬[0, 0] K2 & L1 = K1.ⓑ{I1}V1.