Query Return Results That Contain Duplicates - Only First Or Last Required

I have this query that returns results that contain duplicates(somewhat). I only want either the FIRST or LAST (either one is fine). Here is the query:

select unique PLLA.attribute4, PLA.item_description from po_lines_all PLA, po_line_locations_all PLLA
where PLLA.po_line_id = PLA.po_line_id
and PLLA.attribute4 is not null

So my output is something like this:

RCE12 This is an item for AUL1
RCE13 This is an item for PWEILL
RCE14 This is an item for AUL1

I just want either the RCE12 or RCE14 record and not both since they both have the same description.