#T elim T -T //
qed.
+lemma tw_le_pair_dx (I): ∀V,T. ♯{T} < ♯{②{I}V.T}.
+#I #V #T /2 width=1 by le_S_S/
+qed.
+
(* Basic_1: removed theorems 11:
wadd_le wadd_lt wadd_O weight_le weight_eq weight_add_O
weight_add_S tlt_trans tlt_head_sx tlt_head_dx tlt_wf_ind