  We selected from VLA-FIRST a sample of 94 objects starlike in SDSSS, and with
APM colour O-E>2, i.e. consistent with their being high-z QSOs. 78 candidates
were classified spectroscopically from published data (mainly SDSS) or
observations reported here. The fractions of QSOs (51/78) and z > 3 QSOs
(23/78) are comparable to those found in other photometric searches for high-z
QSOs. We confirm that O-E>2 ensures inclusion of all QSOs with 3.7 < z < 4.4.
The fraction of broad absorption line (BAL) QSOs for 2 < z < 4.4 is 27+-10 per
cent (7/26), and the estimated BAL fraction for radio loud (RL) QSOs is at
least as high as for optically selected QSOs (about 13 per cent). The high BAL
fraction and the high fraction of LoBALs in our sample are likely due to the
red colour selection. The space density of RL QSOs for 3.7 < z < 4.4, MAB (1450
A) < -26.6 and P(1.4 GHz) > 10^25.7 W Hz^(-1) is 1.7+-0.6 Gpc^(-3). Adopting a
RL fraction 13.4+-3 per cent, this corresponds to rho = 12.5+-5.6 Gpc^(-3), in
good agreement with the SDSS QSO luminosity function in Fan et al. (2001). We
note the unusual QSO FIRST 1413+4505 (z=3.11), which shows strong associated
Lyalpha absorption and an extreme observed luminosity, L about 2 x 10^(15)
solar luminosities.
