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1. Cullen, H. F. "Separation Axioms." Ch. 3 in Introduction to General Topology. Boston, MA: Heath, pp. 99-140, 1968.
2. Joshi, K. D. "Separation Axioms." Ch. 7 in Introduction to General Topology. New Delhi, India: Wiley, pp. 159-188, 1983.
3. McCarty, G. Topology, an Introduction with Application to Topological Groups. New York: McGraw-Hill, 1967.
4. Willard, S. "The Separation Axioms." §13 in General Topology. Reading, MA: Addison-Wesley, pp. 85-92, 1970.
5. Referenced on Wolfram|Alpha: Separation Axioms