  Through an optical campaign performed at 4 telescopes located in the northern
and the southern hemispheres, plus archival data from two on-line sky surveys,
we have obtained optical spectroscopy for 28 counterparts of unclassified or
poorly studied hard X-ray emitting objects detected with Swift/BAT and listed
in the 39 months Palermo Swift/BAT hard X-ray catalogue. We have been able to
pinpoint the optical counterpart of these high energy sources by means of X-ray
observations taken with Swift/XRT or XMM which allowed us to restrict the
positional uncertainty from few arcmin to few arcsec; satellite data also
provided information on the X-ray spectra of these objects. We find that 7
sources in our sample are Type 1 AGN while 20 are Type 2 AGN, with their
redshifts lying between 0.009 and 0.075; the remaining object is a Galactic
cataclysmic variable (CV). In this work we provide optical information for all
28 sources and the results of the soft X-ray analysis of 3 out of 5 AGN
observed with XMM/Newton.
