GRB redshift determination in the X–ray band S. Campana, G. Ghisellini, D. Lazzati, F. Haardt and S. Covino Astron. Astrophys. Suppl. Ser., 138 3 (1999) 487-488 Published online: 15 September 1999 DOI: 10.1051/aas:1999322