We thank Helmut Abt and the rest of the NED and SIMBAD groups for their help in defining the reference codes. Table 2 has been prepared with the kind help of Suzanne Laloë at the Institut d'Astrophysique de Paris. NED is a research support program operated by the Jet Propulsion LaboratoryJPL, California Institute of Technology, under contract with the National Aeronautics and Space Administration (Astrophysics Division, Science Operations Branch). SIMBAD is maintained by the Centre de Données astronomiques de Strasbourg, France.