At the time, a new standard epoch (J2000.0) was accepted; followed later by a new reference system with fundamental catalogue (FK5), and expressions for precession of the equinoxes, and in 1979 by new expressions for the relation between Universal Time and sidereal time, and in 1979 and 1980 by a theory of nutation. There were no reliable rotation elements for most planets, but a joint working group on Cartographic Coordinates and Rotational Elements was installed to compile recommended values.