proposition: Lemma Omega : El0 (∀₀¹ i:U⟶₁u0, induct i ⟶₀ i ·₁ WF).
proof: Proof. refine (λ₀¹ i, λ₀ y, _). refine (y·₀[_]·₀_). unfold le,WF,induct. simplify. refine (λ₀¹ x, λ₀ h0, _). simplify. refine (y·₀[_]·₀_). unfold le. simplify. unfold sb at 1. simplify. unfold le' at 1. simplify. exact h0. Qed.