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Category A - Kinematically Confirmed (6 objects)

  1. Spectroscopic evidence must exist for two nearly orthogonal angular momentum vectors with similar amplitudes.

  2. The system must be in an equilibrium or quasi-equilibrium configuration, as shown by the fact that:

    - both components must have similar systemic velocities, and

    - the centers of the two components must be nearly aligned.

  3. The ring must be comparable in size to the inner component, must be luminous (i.e., dust-lane ellipticals are not included), and it must be nearly planar (i.e., the chaotic appearance of M82 would be ruled out).