public function HasFreeShippingVoucher()
    {
        $bHasFreeShipping = false;
        $tmpCurrentPointer = $this->getItemPointer();
        $this->GoToStart();

        while (!$bHasFreeShipping && ($oItem = &$this->Next())) {
            $oVoucherSeries = &$oItem->GetFieldShopVoucherSeries();
            if ($oVoucherSeries->fieldFreeShipping) {
                $bHasFreeShipping = true;
            }
        }
        $this->setItemPointer($tmpCurrentPointer);

        return $bHasFreeShipping;
    }