Correspondent advised. It is OGP policy to maintain within the EPSG dataset the definitions of (i) coordinate reference systems (CRSs), and (ii) transformations between coordinate reference systems. We include within the dataset all component items needed to support CRS and transformation definitions. Conversely, in general we do not include items that do not form part of a CRS included within the dataset. We know of many hundred ellipsoids which have been defined. Most of these have been for purely scientific purposes and never used as part of a coordinate reference system.