4. Modal Logic
We refer Based on Chagrov and Zakharyaschev (1997)A. Chagrov and M. Zakharyaschev, 1997. “Modal Logic”. arXiv:none, Segerberg (1971)K. Segerberg, 1971. An Essay in Classical Modal Logic. Ph.D Thesis, Stanford University, Hudges and Cresswell (2007)G. E. Hudges and M. J. Cresswell, 2007. “A New Introduction to Modal Logic”. arXiv:none, Boolos (1994)G. Boolos, 1994. “The Logic of Provability”. arXiv:none.