  Thanks to the INTEGRAL satellite the way of looking at the hard X-ray sky
above 20 keV has changed substantially. Through the unique imaging and
spectroscopy capabilities of the IBIS instrument that has formed the basis of
the INTEGRAL surveys, this satellite has improved the knowledge on hard X-ray
sources in terms of sensitivity and positional accuracy. Many of the sources
belonging to these surveys are however of unidentified nature, but the combined
use of available information at longer wavelengths (mainly soft X-rays and
radio) and above all optical spectroscopy on the putative counterparts of these
hard X-ray objects can reveal their exact nature. Since 2004 our group
identified more than 100 it INTEGRAL sources, reducing drastically the
percentage of unidentified objects in the various IBIS surveys and allowing
statistical studies on them. Here we present a summary of this identification
work and an outlook of our preliminary results on identification of
newly-discovered sources belonging to the 4th IBIS catalog.
