proposition: Lemma sigma_eq x : x ∈ σ x.
proof: Proof. Proof using M_FST VIEQ. apply sigma_el. now right. Qed.
imports: Undecidability.FOL(Syntax.Facts Semantics.Tarski.FullFacts FST) Undecidability.FOL(Sets.FST) Undecidability.FOL.TRAKHTENBROT(hfs) Undecidability.Shared.Libs.DLW.Utils(finite) Undecidability(Shared.ListAutomation) Coq(Lia)