Natural Deduction for Full S5 Modal Logic with Weak Normalization.

Ana Teresa C. Martins Lília Ramalho Martins Natural Deduction for Full S5 Modal Logic with Weak Normalization. 129-140 2006 143 Electr. Notes Theor. Comput. Sci. http://dx.doi.org/10.1016/j.entcs.2005.05.027 db/journals/entcs/entcs143.html#MartinsM06