+fact lveq_inv_zero_aux: ∀L1,L2,n1,n2. L1 ≋ⓧ*[n1, n2] L2 →
+ 0 = n1 → 0 = n2 →
+ ∨∨ ∧∧ ⋆ = L1 & ⋆ = L2
+ | ∃∃I1,I2,K1,K2. K1 ≋ⓧ*[0, 0] K2 & K1.ⓘ{I1} = L1 & K2.ⓘ{I2} = L2.
+#L1 #L2 #n1 #n2 * -L1 -L2 -n1 -n2
+[1: /3 width=1 by or_introl, conj/
+|2: /3 width=7 by ex3_4_intro, or_intror/
+|*: #K1 #K2 #n #_ #H1 #H2 destruct
+]
+qed-.
+
+lemma lveq_inv_zero: ∀L1,L2. L1 ≋ⓧ*[0, 0] L2 →
+ ∨∨ ∧∧ ⋆ = L1 & ⋆ = L2
+ | ∃∃I1,I2,K1,K2. K1 ≋ⓧ*[0, 0] K2 & K1.ⓘ{I1} = L1 & K2.ⓘ{I2} = L2.
+/2 width=5 by lveq_inv_zero_aux/ qed-.
+
+fact lveq_inv_succ_sn_aux: ∀L1,L2,n1,n2. L1 ≋ⓧ*[n1, n2] L2 →
+ ∀m1. ↑m1 = n1 →
+ ∃∃K1. K1 ≋ⓧ*[m1, 0] L2 & K1.ⓧ = L1 & 0 = n2.
+#L1 #L2 #n1 #n2 * -L1 -L2 -n1 -n2
+[1: #m #H destruct
+|2: #I1 #I2 #K1 #K2 #_ #m #H destruct
+|*: #K1 #K2 #n #HK #m #H destruct /2 width=3 by ex3_intro/
+]
+qed-.
+
+lemma lveq_inv_succ_sn: ∀L1,K2,n1,n2. L1 ≋ⓧ*[↑n1, n2] K2 →
+ ∃∃K1. K1 ≋ⓧ*[n1, 0] K2 & K1.ⓧ = L1 & 0 = n2.
+/2 width=3 by lveq_inv_succ_sn_aux/ qed-.
+
+lemma lveq_inv_succ_dx: ∀K1,L2,n1,n2. K1 ≋ⓧ*[n1, ↑n2] L2 →
+ ∃∃K2. K1 ≋ⓧ*[0, n2] K2 & K2.ⓧ = L2 & 0 = n1.
+#K1 #L2 #n1 #n2 #H
+lapply (lveq_sym … H) -H #H
+elim (lveq_inv_succ_sn … H) -H /3 width=3 by lveq_sym, ex3_intro/
+qed-.
+
+fact lveq_inv_succ_aux: ∀L1,L2,n1,n2. L1 ≋ⓧ*[n1, n2] L2 →
+ ∀m1,m2. ↑m1 = n1 → ↑m2 = n2 → ⊥.