We presented a general classification scheme for the tripartite L×N×N entangled system under stochastic local operation and classical
communication. The whole classification procedure consists of two correlated
parts: the simultaneous similarity transformation of a commuting matrix pair
into a canonical form and the study of internal symmetry of parameters in the
canonical form. Based on this scheme, a concrete example of entanglement
classification for a 3×N×N system is given.Comment: 21 pages; published in Phys. Rev.