I collect several RSS feeds for a "Local news" block. Unfortunately there is a content provider that delivers:

http://example.com/index.php?aid=123
http://example.com/index.php?aid=456
http://example.com/index.php?aid=789

The next time new articles are pulled I get something like:

http://www.example.com/index.php?aid=123
http://www.example.com/index.php?aid=456
http://www.example.com/index.php?aid=789

(same as above, only with www). Therefore each entry is in my list twice.

Any ideas how to solve this issue?