  We present the results of our optical spectrophotometric campaign ongoing at
the Astronomical Observatory of Bologna in Loiano (Italy) on hard X-ray sources
detected by INTEGRAL. We observed spectroscopically the putative optical
counterparts of four more INTEGRAL sources, IGR J12391-1610, IGR J18406-0539,
2E 1853.7+1534 and IGR J19473+4452. These data have allowed us to determine
their nature, finding that IGR J12391-1610 (=LEDA 170194) and IGR J19473+4452
are Seyfert 2 galaxies at redshifts z = 0.036 and z = 0.053, respectively, IGR
J18406-0539 (=SS 406) is a Be massive X-ray binary located at about 1.1 kpc
from Earth, and 2E 1853.7+1534 is a Type 1 Seyfert galaxy with z = 0.084.
Physical parameters for these objects are also evaluated by collecting and
discussing the available multiwavelength information. The determination of the
extragalactic nature of a substantial fraction of sources inside the INTEGRAL
surveys underlines the importance of hard X-ray observations for the study of
background Active Galactic Nuclei located beyond the `Zone of Avoidance' of the
Galactic Plane.
