A pulse phase-dependent spectroscopic study of Vela X–1 in the 8–100 keV band A. La Barbera, A. Santangelo, M. Orlandini and A. Segreto A&A, 400 3 (2003) 993-1005 Published online: 07 March 2003 DOI: 10.1051/0004-6361:20030010