Dietmar Berwanger Krishnendu Chatterjee Martin De Wulf Laurent Doyen Thomas A. Henzinger Alpaga: A Tool for Solving Parity Games with Imperfect Information http://arxiv.org/abs/0901.4728 2009 CoRR abs/0901.4728 db/journals/corr/corr0901.html#abs-0901-4728 informal publication