Optical spectroscopy of 1Jy, S4 and S5 radio sources. IV.

The results of optical spectroscopy of 23 radio sources from the 1 Jy, S4, and S5 radio surveys are presented. New redshifts have been measured for 16 optical counterparts including a few objects, where spectral features with ambiguous identifications had previously been observed. For the gravitational lens candidate 0218+357, a lower limit for the redshift of z > 0.656 has been derived from narrow absorption lines. Several objects show featureless optical spectra, including a new, previously unknown BL Lac candidate. Direct imaging data are provided for a number of sources of special interest or with existing ambiguities about their identification.