public static function Atci13($rc, $dc, $pr, $pd, $px, $rv, $date1, $date2,
          &$ri, &$di, &$eo) {

    /* Star-independent astrometry parameters */
    $astrom = new iauASTROM();

    /* The transformation parameters. */
    IAU::Apci13($date1, $date2, $astrom, $eo);

    /* ICRS (epoch J2000.0) to CIRS. */
    IAU::Atciq($rc, $dc, $pr, $pd, $px, $rv, $astrom, $ri, $di);

    /* Finished. */
  }