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3. M. Dummett, Frege and other Philosophers, Oxford: Clarendon Press, 1991, p. 80.
4. G. Frege, Nachgelassene Schriften, ed. H. Hermes, F. Kambartel, F. Karlbad. Hamburg: 1969, p. 115
5. G. Frege, Kleine Schriften, ed. I. Angeleli. Hildesheim: G.Olms, 1967, p. 359.