The BeppoSAX High Energy Large Area Survey - IV. On the soft X-ray properties of the hard X-ray-selected HELLAS sourcesC. Vignali, A. Comastri, F. Fiore and F. La FrancaA&A, 370 3 (2001) 900-908DOI: https://doi.org/10.1051/0004-6361:20010286
