+
+(* Basic inversion lemmas ***************************************************)
+
+lemma destruct_lpair_lpair: ∀I1,I2,L1,L2,V1,V2. L1.ⓑ{I1}V1 = L2.ⓑ{I2}V2 →
+ ∧∧L1 = L2 & I1 = I2 & V1 = V2.
+#I1 #I2 #L1 #L2 #V1 #V2 #H destruct /2 width=1/
+qed-.
+
+lemma discr_lpair_x_xy: ∀I,V,L. L = L.ⓑ{I}V → ⊥.
+#I #V #L elim L -L
+[ #H destruct
+| #L #J #W #IHL #H
+ elim (destruct_lpair_lpair … H) -H #H1 #H2 #H3 destruct /2 width=1/ (**) (* destruct lemma needed *)
+]
+qed-.
+
+(* Basic_1: removed theorems 2: chead_ctail c_tail_ind *)