Discovery of heavily-obscured AGN among seven INTEGRAL hard X-ray sources observed by ChandraS. Sazonov, M. Revnivtsev, R. Burenin, E. Churazov, R. Sunyaev, W. R. Forman and S. S. MurrayA&A, 487 2 (2008) 509-517DOI: https://doi.org/10.1051/0004-6361:200809528