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References
- ↑ Moschovakis, Y. N. (1987), Descriptive Set Theory, Studies in Logic and the Foundations of Mathematics, Elsevier, p. 158, ISBN 9780080963198 .
- ↑ Gabbay, Dov M.; Kanamori, Akihiro; Woods, John (2012), Sets and Extensions in the Twentieth Century, Handbook of the History of Logic, 6, Elsevier, p. 465, ISBN 9780080930664 .
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