Query to Get AP Invoice Duplicate Audit Details in Oracle Applications

Following query pull out the details of  Account Payable Duplicate invoice details  

SELECT DISTINCT a.invoice_id,

                  c.vendor_name,

                  c.segment1 vendor_numder,

                  a.invoice_num,

                  a.invoice_amount,

                  a.amount_paid,

                  TO_CHAR (a.invoice_date, 'DD-MON-YYYY') invoice_date,

                  a.payment_status_flag,

                  (SELECT user_name

                     FROM apps.fnd_user

                    WHERE user_id = a.created_by)

                     inv_created_by,

                  TO_CHAR (a.creation_date, 'DD-MON-YYYY') creation_date,

                  TO_CHAR (a.CANCELLED_DATE, 'DD-MON-YYYY') CANCELLED_DATE,

                  (SELECT name

                     FROM apps.hr_operating_units

                    WHERE organization_id = a.org_id)

                     operating_unit

    FROM apps.ap_invoices_all a, apps.ap_invoices_all b, apps.ap_suppliers c

   WHERE     a.vendor_id = b.vendor_id

         AND a.invoice_id <> b.invoice_id

         AND a.vendor_id = c.vendor_id

         AND a.invoice_date = b.invoice_date

         AND a.invoice_amount = b.invoice_amount

         AND (INSTR (a.invoice_num, b.invoice_num) >= 1

              OR INSTR (b.invoice_num, a.invoice_num) >= 1)

ORDER BY a.invoice_num