  The local physical properties of an isolated quantum statistical system in
the stationary state reached long after a quench are generically described by
the Gibbs ensemble, which involves only its Hamiltonian and the temperature as
a parameter. If the system is instead integrable, additional quantities
conserved by the dynamics intervene in the description of the stationary state.
The resulting generalized Gibbs ensemble involves a number of temperature-like
parameters, the determination of which is practically difficult. Here we argue
that in a number of simple models these parameters can be effectively
determined by using fluctuation-dissipation relationships between response and
correlation functions of natural observables, quantities which are accessible
in experiments.
