Takashi Matsuhisa Ibaraki National College of Technology   Nakane 866 Hitachinaka-shi, Ibaraki 312-8508 Japan   mathisa@ge.ibaraki-ct.ac.jp         Primary Research Focus: Knowledge, common-knowledge, Hash equilibrium, communication, learning, rational expectation and trade   JEL Areas: C7 : Game Theory and Bargaining Theory:General D5 : General Equilibrium and Disequilibrium: General