  The Rashba and Dresselhaus spin-orbit interactions are both shown to yield
the low temperature spin-Hall effect for strongly localized electrons coupled
to phonons. A frequency-dependent electric field ${\bf E}(\omega)$ generates a
spin-polarization current, normal to ${\bf E}$, due to interference of hopping
paths. At zero temperature the corresponding spin-Hall conductivity is real and
is proportional to $\omega^{2}$. At non-zero temperatures the coupling to the
phonons yields an imaginary term proportional to $\omega$. The interference
also yields persistent spin currents at thermal equilibrium, at ${\bf E}=0$.
The contributions from the Dresselhaus and Rashba interactions to the
interference oppose each other.
