Galaxy Dynamics and the PNe Population
  This review attempts to place the observations of extragalactic planetary nebulae in the context of galactic dynamics. From this point of view only the radial velocities of the PNe are important. We have built a specialised instrument to detect PNe in distant galaxies and measure their radial velocities in one step. This is explained in some detail, along with classical techniques for obtaining kinematic information. The review includes a vision of possible future developments in the field. 
Nigel G. Douglas