1. Balcázar, J., Díaz, J. and Gabarró, J., 1988,Structural Complexity I, EATCS Monographs on Theoretical Computer Science 11, Berlin: Springer Verlag.
2. Ben-Ari, M., Halpern, J. and Pnueli, A., 1982, ?Deterministic propositional dynamic logic: finite models, complexity and completeness?,Journal of Computer and System Sciences 25, 402?417.
3. Berger, R., 1966, ?The undecidability of the dominoe problem?,Mem. Amer. Math. Soc. 66, 1?72.
4. Blackburn, P., 1989, ?Nominal tense logic?, to appear inNotre Dame Journal of Formal Logic.
5. Studies in Logic, Language and Information;P. Blackburn,1991