Nonsequential positive-operator-valued measurements on entangled mixed states do not always violate a Bell inequality

We present a local-hidden-variable model for positive-operator-valued measurements (an LHVPOV model) on a class of entangled generalized Werner states, thus demonstrating that such measurements do not always violate a Bell-type inequality. We also show that, in general, if the state rho(') can be obtained from rho with certainty by local quantum operations without classical communication, then an LHVPOV model for the state rho implies the existence of such a model for rho(').