Chow Liu Tree is capture both dependencies across time and dependencies across variables. Chow Liu Tree structures in the context of providing improved, yet tractable, models to address these problems in capturing output dependencies for HMMs. This article actually focus on Chow Liu Tree, which is under the assumption that they are a generally useful modeling technique in the context of multivariate time dependent data. Generalizations of the Chow Liu Tree are the so called t-cherry junction trees.