Optical spectroscopic observations of gamma-ray blazar candidates VIII:
  the 2016-2017 follow up campaign carried out at SPM, NOT, KPNO and SOAR
  telescopes
  The third Fermi source catalog lists 3033 gamma-ray sources above $4\sigma$
significance. More than 30% are classified as either unidentified/unassociated
Gamma-ray sources (UGSs), with about 20% classified as Blazar candidates of
uncertain types (BCUs). To confirm the blazar-like nature of candidate
counterparts of UGSs and BCUs, we started in 2012 an optical spectroscopic
follow up campaign. We report here the spectra of 36 targets with observations
from the Observatorio Astron\'omico Nacional San Pedro M\'artir, the Southern
Astrophysical Research Observatory, the Kitt Peak National Observatory and the
Northern Optical Telescope, between 2016 and 2017. We confirm the BL Lac nature
of 23 sources, and the flat spectrum radio quasar nature of other 7 ones. We
also provide redshift estimates for 19 out of these 30 confirmations, with only
one being a lower limit due to spectral features ascribable to intervening
systems along the line of sight. As in previous analyses, the largest fraction
of now-classified BCUs belong to the class of BL Lac objects, that appear to be
the most elusive class of active galactic nuclei. One of the BL Lacs identified
in this work, associated with 3FGL J2213.6-4755, lies at a redshift of
$z>$1.529, making it one of the few distant gamma-ray BL Lac objects.
