Which table holds information showing invoices and the POs they are matched to?

Hi,

Using SQL Developer, I need to extract data showing invoices together with the POs they have been matched to. More than one invoice can be matched to a PO, so I expect to see records showing the same PO number against more than one invoice.  In the same query I need to extract the PO number, receipt number and invoice number for each record where applicable.  Can some tell me which table holds invoices together with the POs they matched to?  And how this can be linked to the PO_Headers table?

Thanks

Winnie