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3. Johnstone, P.T. 1982. Stone spaces, Cambridge Studies in Advanced Mathematics, no. 3, Cambridge, UK: Cambridge University Press.
4. Johnstone, P.T. 2002a. Sketches of an elephant: A topos theory compendium, vol. 1, Oxford Logic Guides, no.44, Oxford: Oxford University Press.
5. Johnstone, P.T. 2002b. Sketches of an elephant: A topos theory compendium, vol. 2, Oxford Logic Guides, no. 44, Oxford: Oxford University Press.