Mac Lane, Saunders (1971), "Categorical algebra and set-theoretic foundations", Axiomatic Set Theory (Proc. Sympos. Pure Math., Vol. XIII, Part I, Univ. California, Los Angeles, Calif., 1967), Providence, RI: Amer. Math. Soc., pp. 231–240, MR0282791. "The working mathematicians usually thought in terms of a naive set theory (probably one more or less equivalent to ZF) ... a practical requirement [of any new foundational system] could be that this system could be used "naively" by mathematicians not sophisticated in foundational research" (p. 236).
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Mac Lane, Saunders (1971), "Categorical algebra and set-theoretic foundations", Axiomatic Set Theory (Proc. Sympos. Pure Math., Vol. XIII, Part I, Univ. California, Los Angeles, Calif., 1967), Providence, RI: Amer. Math. Soc., pp. 231–240, MR0282791. "The working mathematicians usually thought in terms of a naive set theory (probably one more or less equivalent to ZF) ... a practical requirement [of any new foundational system] could be that this system could be used "naively" by mathematicians not sophisticated in foundational research" (p. 236).
Letters from Cantor to Richard Dedekind on August 3, 1899 and on August 30, 1899, Zermelo 1932 p. 448 (System aller denkbaren Klassen) and Meschkowski & Nilson 1991 p. 407. (There is no set of all sets.) Zermelo, Ernst (1932), Georg Cantor: Gesammelte Abhandlungen mathematischen und philosophischen Inhalts. Mit erläuternden Anmerkungen sowie mit Ergänzungen aus dem Briefwechsel Cantor-Dedekind. Edited by the author., Berlin: Springer Meschkowski, Herbert[in German]; Nilson, Winfried (1991), Georg Cantor: Briefe. Edited by the authors., Berlin: Springer, ISBN3-540-50621-7
