∀ b, a. ¬(b ∈ x0 ∧ ordered≤(a ' + x0) ∧ b < a), b ∈ a0 + x0, ordered≤(a ' + (a0 + x0)), b < a ⊦
Used simplifier rules: list freely generated by [], +;;%in-empty: ⊦ ¬ a ∈ []; from specification list