Vignali, C.C.VignaliComastri, A.A.ComastriFiore, F.F.Fiore2020-09-172020-09-172001-01-01https://hdl.handle.net/20.500.13025/99Memorie della Societ Astronomica Italiana (ISSN 0037-8720), Vol. 72, N. 1, p. 183 - 185 (2001). In AGN in the year 2000. Fourth National Meeting on Active Galactic Nuclei, Trieste, 15 - 18 May 2000, edited by A. CelottiThe main properties of the HELLAS survey are briefly outlined. In particular, the suggestion of a dichotomy between the optical and the X-ray classification will be discussed. A comparison between the HELLAS sources soft X-ray properties and the ROSAT-selected objects is also described.http://adsabs.harvard.edu/abs/2001MmSAI..72..183V2001MmSAI..72..183V