+
+(* Basic_2A1: was: lprs_inv_pair2 *)
+lemma lprs_inv_pair_dx (h) (G):
+ ∀I,L1,K2,V2. ⦃G, L1⦄ ⊢ ➡*[h] K2.ⓑ{I}V2 →
+ ∃∃K1,V1. ⦃G, K1⦄ ⊢ ➡*[h] K2 & ⦃G, K1⦄ ⊢ V1 ➡*[h] V2 & L1 = K1.ⓑ{I}V1.
+/2 width=1 by lex_inv_pair_dx/ qed-.
+
+(* Basic eliminators ********************************************************)
+
+(* Basic_2A1: was: lprs_ind_alt *)
+lemma lprs_ind (h) (G): ∀R:relation lenv.
+ R (⋆) (⋆) → (
+ ∀I,K1,K2.
+ ⦃G, K1⦄ ⊢ ➡*[h] K2 →
+ R K1 K2 → R (K1.ⓘ{I}) (K2.ⓘ{I})
+ ) → (
+ ∀I,K1,K2,V1,V2.
+ ⦃G, K1⦄ ⊢ ➡*[h] K2 → ⦃G, K1⦄ ⊢ V1 ➡*[h] V2 →
+ R K1 K2 → R (K1.ⓑ{I}V1) (K2.ⓑ{I}V2)
+ ) →
+ ∀L1,L2. ⦃G, L1⦄ ⊢ ➡*[h] L2 → R L1 L2.
+/3 width=4 by lex_ind/ qed-.