Multifrequency study of gigahertz-peaked spectrum sources with RATAN-600
  We report the radio continuum properties for several samples of peaked
spectrum (PS) radio sources. Broadband spectra of the objects were analysed
using the RATAN-600 six-frequency (1.2-22 GHz) observations and available
literature data, obtained on a time scale of 20-30 years. We discuss
statistical differences in radio properties for several AGN types with peaked
spectra and focus on PS quasars at high redshifts ($z > 3$). We confirm that a
relatively small fraction (1-2%) of bright PS sources can be considered as
genuine GPSs when they have been monitored densely and for a long time. The
contamination of GPS source samples by blazars is getting stronger as the
redshift increases, and we confirm that it is underestimated due to lack of
systematic multifrequency observations.
