A CUT FREE SIMPLE SEQUENT CALCULUS FOR MODAL LOGIC S5
In this paper, we present a simple sequent calculus for the modal propositional logic S5. We prove that this sequent calculus is theoremwise equivalent to the Hilbert style system S5, that it is contraction free and cut free, and finally that it is decidable. All results are proved in a purely syntactic way.
The Review of Symbolic Logic