The field studied is part of the Hamburg Quasar Survey (Engels et al. 1988, PASPC 2, 143). It contains a spatially and magnitude (down to ∼ 18.m5) complete AGN sample. Several follow-up observations were made: a deep radio continuum survey at 21 cm and 74 cm, a HI survey and a ROSAT survey consisting of 48 overlapping PSPC pointings with .
