  We report the observation of a resonance in the microwave spectra of the real
diagonal conductivities of a two-dimensional electron system within a range of
~ +- .0.015 $ from filling factor $\nu=1/3$. The resonance is remarkably
similar to resonances previously observed near integer $\nu$, and is
interpreted as the collective pinning mode of a disorder-pinned Wigner solid
phase of $e/3$-charged carriers .
