E_4

Definition

• A topological space (X, τ) is called an E_4 space if X has a σ-point finite base.

Reference

• Aull, C. E., "Some base axioms for topology involving enumerability.", 1971 General Topology and its Relations to Modern Analysis and Algebra, III (Proc. Conf., Kanpur, 1968) pp. 55-61.