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2. Dryer, D. P., Kant’s Solution for Verification in Metaphysics, Allen & Unwin, London 1966.
3. Hintikka, Jaakko, Models for Modalities, Reidel, Dordrecht, 1969.
4. Hintikka, Jaakko, ‘“Dinge an sich” Revisited’, in Hintikka, Jaakko, Knowledge and the Known, Reidel, Dordrecht, 1974, pp. 197–211.
5. Hintikka, Jaakko, ‘Information, Causality, and the Logic of Perception’, in Hintikka, Jaakko, The Intentions of Intentionality and Other New Models for Modalities, Reidel, Dordrecht, 1975, pp. 59–75.