1. Selective separability: general facts and behaviour in countable spaces;Bella;Topology Proceedings,2008
2. N. Dunford and J. T. Schwartz, Linear Operators, Part I, John Wiley and Sons, New York, 1976.
3. ON SPACES CO-ABSOLUTE WITH METRIC SPACES
4. W. Rudin, Real and Complex Analysis, MacGraw-Hill, Ljubljana, 1970. L. A. Steen and J. A. Seebach, Counterexamples in Topology, Holt, Rinehart and Winston, Inc., New York, 1970. A. Tesei, Istituzioni di Analisi Superiore, Bollati Boringhieri, Torino, 1997.
5. COMBINATORICS OF OPEN COVERS VI: SELECTORS FOR SEQUENCES OF DENSE SETS