"Categorical algebra and set-theoretic foundations", Axiomatic Set Theory (Proc. Sympos. Pure Math., Vol. XIII, Part I, Univ. California, Los Angeles, Calif., 1967), Amer. Math. Soc., Providence, R.I., 1971, ss. 231-240. "The working mathematicians usually thought in terms of a naïve 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 "naïvely" by mathematicians not sophisticated in foundational research" (p. 236).
