  We used the Australia Telescope Compact Array (ATCA) to obtain 40 GHz and 95
GHz observations of a number of sources that were selected from the Australia
Telescope Compact Array 20 GHz (AT20G) survey . The aim of the observations was
to improve the spectral coverage for sources with spectral peaks near 20 GHz or
inverted (rising) radio spectra between 8.6 GHz and 20 GHz. We present the
radio observations of a sample of 21 such sources along with optical spectra
taken from the ANU Siding Spring Observatory 2.3m telescope and the ESO-New
Technology Telescope (NTT). We find that as a group the sources show the same
level of variability as typical GPS sources, and that of the 21 candidate GPS
sources roughly 60% appear to be genuinely young radio galaxies. Three of the
21 sources studied show evidence of being restarted radio galaxies. If these
numbers are indicative of the larger population of AT20G radio sources then as
many as 400 genuine GPS sources could be contained within the AT20G with up to
25% of them being restarted radio galaxies.
