  Choosing four entangled stets to form an orthogonal and complete basis for a
two-particle system, we argue that a local hidden variable model should give
the probability of each entangled state if the two-particle system is described
by a mixed state. Under this condition, a new Bell inequality is derived for
the Werner states, and a nonlocality proof can be given for nonsequential
measurements PACS number: 03.65.Bz
