11i AP invoice lines reference_1 and reference_2 columns

Hi

  I am working with some old data which is now been migrated to R12 but was initially entered in 11i.  There are some AP invoices that I am trying to link to PO receipts/shipments.

The Ap invoice header, lines and distributions do not contain any PO related information but the reference_1 and reference_2 columns of the AP invoice lines are populated. Upon checking I found the values in these columns do not correspond to PO header or PO lines or the Receiving transaction information.

Could anyone help me with any information about this?

Thanks