private function getEntryFields(Source $source, BaseAcumulusEntry $localEntryInfo, array $entry)
    {
        /* keys in $entry array:
         *   - entryid
         *   * entrydate: yy-mm-dd
         *   - entrytype
         *   - entrydescription
         *   - entrynote
         *   - fiscaltype
         *   * vatreversecharge: 0 or 1
         *   * foreigneu: 0 or 1
         *   * foreignnoneu: 0 or 1
         *   * marginscheme: 0 or 1
         *   * foreignvat: 0 or 1
         *   - contactid
         *   - accountnumber
         *   - costcenterid
         *   - costtypeid
         *   * invoicenumber
         *   - invoicenote
         *   - descriptiontext
         *   - invoicelayoutid
         *   - totalvalueexclvat
         *   - totalvalue
         *   - paymenttermdays
         *   * paymentdate: yy-mm-dd
         *   * paymentstatus: 1 or 2
         *   * deleted: timestamp
         */
        $fields = $this->getVatTypeField($entry)
            + $this->getAmountFields($source, $entry)
            + $this->getPaymentStatusFields($source, $entry)
            + $this->getLinksField($localEntryInfo->getToken());

        return $fields;
    }