Listing name of purchase order attachments in a report

Summary

OTBI subject areas do not provide the filenames of attached documents

Content

I need to produce a report that lists the names of all the attachments for purchase orders for audit purposes.  This would be done for purchase orders created in a certain time frame or range of PO numbers.  I can not find any fields in the subject areas other than the reference to notes to approver or supplier. 

I have not been able to identify the tables I need to access in order to create a data model that would contain this information.  Can someone provide some assistance with identifying the tables I would need to access?