Gaia GraL: Gaia DR2 Gravitational Lens Systems. VI. Spectroscopic
  Confirmation and Modeling of Quadruply-Imaged Lensed Quasars
  Combining the exquisite angular resolution of Gaia with optical light curves
and WISE photometry, the Gaia Gravitational Lenses group (GraL) uses machine
learning techniques to identify candidate strongly lensed quasars, and has
confirmed over two dozen new strongly lensed quasars from the Gaia Data Release
2. This paper reports on the 12 quadruply-imaged quasars identified by this
effort to date, which is approximately a 20% increase in the total number of
confirmed quadruply-imaged quasars. We discuss the candidate selection,
spectroscopic follow-up, and lens modeling. We also report our spectroscopic
failures as an aid for future investigations.
