Spectroscopic observations of radio source identifications from the 1 Jy, S4 and S5 surveys. III

Optical spectra are presented for the optical counterparts of 21 radio sources taken from the 1 Jy, S4, and S5 radio source catalogues. New redshifts are given for 18 sources, including a radio-selected quasar with a redshift of z = 3.886. For two other sources, redshifts had previously been listed in other publications and were confirmed by the new observations. Finally, one radio source is confirmed as a BL Lac object showing a featureless spectrum. For several sources, additional direct imaging data are provided