public static function Apci($date1, $date2, array $ebpv, array $ehp, $x, $y,
          $s, iauASTROM &$astrom) {

    /* Star-independent astrometry parameters for geocenter. */
    IAU::Apcg($date1, $date2, $ebpv, $ehp, $astrom);

    /* CIO based BPN matrix. */
    IAU::C2ixys($x, $y, $s, $astrom->bpn);

    /* Finished. */
  }