NASA and CDS Strasbourg were the first institutions to systematically collect machine-readable versions of astronomical catalogs. These two centers are very comprehensive for ground-based astronomical catalogs, and they have a common agreement to mutually exchange their newly acquired data sets, including a common 4-digit numbering system. However, many other interesting catalogs are not available from these two centers. Some of them can be found within various other databases (e.g., DIRA2, EINLINE, EXOSAT, HEASARC, STARCAT, STARLINK). Bulk tabular data published in ApJ, ApJS, AJ and PASP are issued on CD-ROM (see Abt 1993), while those published in A&Aor A&ASare stored by CDS (see A&A280, 1 or A&AS103, 1).