Double-Negation Elimination in Some Propositional Logics

Michael Beeson Robert Veroff Larry Wos Double-Negation Elimination in Some Propositional Logics http://arxiv.org/abs/cs.LO/0301026 2003 CoRR cs.LO/0301026 db/journals/corr/corr0301.html#cs-LO-0301026 informal publication