INTEGRAL/IBIS observations of vela X-1 in a flaring state. Staubert, R; Kreykenbohm, I; Kretschmar, P; Chernyakova, M; Pottschmidt, K; Benlloch-Garcia, S; Wilms, J; Santangelo, A; Segreto, A; V Kienlin, A; Sidoli, L; Larsson, S; Westergaard, N. European Space Agency, (Special Publication) ESA SP 2004