  All-sky explorations by Fermi-LAT have revolutionized our view of the
gamma-ray sky. While its ongoing all-sky survey counts thousands of sources,
essential issues related to the nature of unassociated sources call for
sensitive all-sky surveys at hard X-ray energies that allow for their
identification. We present the results of the association of the Fermi-LAT
second source catalog to hard X-ray detected sources.
