Query to get PO, Invoice, Receipt number

SELECT DISTINCT pha.segment1 po_number ,
  aia.invoice_num invoice_number ,
  rsh.receipt_num receipt_number
FROM po_headers_all pha ,
  po_distributions_all pda ,
  ap_invoice_distributions_all aid ,
  ap_invoices_all aia ,
  rcv_shipment_lines rsl ,
  rcv_shipment_headers rsh
WHERE pha.po_header_id    =pda.po_header_id
AND aid.po_distribution_id=pda.po_distribution_id
AND aia.invoice_id        =aid.invoice_id
AND rsl.po_header_id      =pha.po_header_id
AND rsl.shipment_header_id=rsh.shipment_header_id
AND pha.segment1          =NVL(:P_PO_NUM,pha.segment1)
AND aia.invoice_num       =NVL(:P_INVOICE_NUM,aia.invoice_num)
AND rsh.receipt_num       =NVL(:P_RECEIPT_NUM,rsh.receipt_num) ;