Discovery of radio-loud quasars with redshifts above 4 from the PMN sample I. M. Hook, R. G. McMahon, P. A. Shaver and I. A. G. Snellen A&A, 391 2 (2002) 509-517 Published online: 02 August 2002 DOI: 10.1051/0004-6361:20020869