proposition: Lemma phi0_zero : phi0 zero = 1.
proof: Proof. generalize (ordering_function_least_least phi0_ordering),least_AP; intros H H0; rewrite (least_member_unicity AX1 H H0);eauto. Qed.
imports: Coq(Arith Logic.Epsilon Ensembles Lia) ZornsLemma(CountableTypes)