Delete duplicate subtrees?

[David Rogers]

Hello

I've copied text from several different sources into an org 
buffer, and now I find I have a large number of subtrees that are 
exactly the same. All headlines are at the top level, so there are 
no duplicates at different levels from each other - but there 
*are* some where the headline matches but the contents don't 
match. Is there an efficient way to delete all-but-one of the 
exactly duplicate subtrees, but avoid deleting any whose contents 
are different? (When the large number of exact duplicates are 
gone, it will be easy for me to resolve the partial matches one by 
one.)

--
Thanks
David