1. C. E. Aull: A Class of Topological Spaces. Prace Matematyczne (to appear).
2. Closed Set Countability Axioms;Aull;Indagationes Math.,1966
3. Metrization of Topological Spaces;Bing;Can. Math. J.,1951
4. Metrizability of Countable Unions;Corson;Illinois Math. J.,1964
5. On Countably Paracompact Spaces;Dowker;Can. Math. J.,1951