2XMM J083026+524133: the most X-ray luminous cluster at redshift 1 G. Lamer, M. Hoeft, J. Kohnert, A. Schwope and J. Storm A&A, 487 2 (2008) L33-L36 Published online: 01 July 2008 DOI: 10.1051/0004-6361:200810255