  Based on our previous QCD sum rule studies on hidden-charm pentaquark states,
we discuss possible interpretations of the $P_c(4312)$, $P_c(4440)$, and
$P_c(4457)$, which were recently observed by LHCb. Our results suggest that the
$P_c(4312)$ can be well interpreted as the $[\Sigma_c^{++} \bar D^-]$ bound
state with $J^P = 1/2^-$, while the $P_c(4440)$ and $P_c(4457)$ can be
interpreted as the $[\Sigma_c^{+} \bar D^0]$ bound state with $J^P = 1/2^-$,
the $[\Sigma_c^{*++} \bar D^{-}]$ and $[\Sigma_c^{+} \bar D^{*0}]$ bound states
with $J^P = 3/2^-$, or the $[\Sigma_c^{*+} \bar D^{*0}]$ bound state with $J^P
= 5/2^-$. We propose to measure their spin-parity quantum numbers to verify
these assignments.
