1. Bailhache, P.: Essai de logique déontique. Vrin, (1991)
2. Chellas, B.: Modal Logic: an Introduction. Cambridge University Press, (1980)
3. Demri, S.: The validity problem for the logic DALLA is decidable. Bulletin of the Polish Academy of Sciences, 4, (1996), 79–86
4. Demri, S. and Orlowska, E.: Logical analysis of indiscernability. ICS Research Report 11/96, (1996), Warsaw University of Technology. See also chapter 11.
5. Fagin, R., Halpern, J., Moses, Y. and Vardi, M.: Reasoning About Knowledge. MIT Press, (1995)