1. Aczel, P., ?Lectures notes on non-well-founded sets?, 198+ (forthcoming).
2. Barwise, J. and Etchemendy, J., the Liar: An Essay on Truth and Circular Propositions, 198+ (forthcoming).
3. CarnapR., Meaning and Necessity, The University of Chicago Press, Chicago, 1947.
4. CresswellM. J., Structured Meanings: The Semantics of Propositional Attitudes, The MIT Press, Cambridge MA, 1985.
5. CresswellM. J., Logics and Languages, Methuen, London, 1973.