select distinct and ordered from two graphs

Hi,
I wonder how to solve this. I have the following query:

SELECT ?labelValue FROM :graphA FROM :graphB
WHERE {	
  ?post :contains :givenTag .
  ?post :contains ?tag .
  ?tag :label ?labelValue .
  ?post :created ?date
  }
ORDER BY DESC (?date)
LIMIT 10

Now, I would like to have only distinct ?labelValues as results.  
Unfortunately, in my case SELECT DISTINCT messes up the order when  
selecting from several graphs.

How could I make the results (?labelValue) of the above query distinct  
while keeping the order?

Thanks,
Mirko