Bimodal spectral variability of Cygnus X-1 in an intermediate state J. Malzac, P. O. Petrucci, E. Jourdain, M. Cadolle Bel, P. Sizun, G. Pooley, C. Cabanac, S. Chaty, T. Belloni, J. Rodriguez et al. (4 more) A&A, 448 3 (2006) 1125-1137 Published online: 03 March 2006 DOI: 10.1051/0004-6361:20053614