  Perfect fluid Friedmann-Robertson-Walker quantum cosmological models for an
arbitrary barotropic equation of state $p = \alpha\rho$ are constructed using
Schutz's variational formalism. In this approach the notion of time can be
recovered. By superposition of stationary states, finite-norm wave-packet
solutions to the Wheeler-DeWitt equation are found. The behaviour of the scale
factor is studied by applying the many-worlds and the ontological
interpretations of quantum mechanics. Singularity-free models are obtained for
$\alpha < 1$. Accelerated expansion at present requires $- 1/3 > \alpha > - 1$.
