One week ago, I asked a question on math.stackexchange.com (http://math.stackexchange.com/questions/209120/a-question-on-intuitionistc-propositional-logic). But nobody answered my question. So I present it here:
In the Kripke's semantics of intuitionistic propositional logic, the frames are all partially ordered frames. Prove that:
Two finite-rooted frames are isomorphic iff they validate the same formulas in the language of intuitionistic propositional logic.
Thanks very much.