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Yea as Highland and Marcelo basically said it, if it's Duplicate content than the only thing you can really do is place a canonical tag, or just rewrite the content. Now I think from what Steve and I are getting from your question is that, you have "similar" content not the "same" content but "similar" content on your website.  If it's similar content than I would simply try to add more content on one of the pages, or just rewrite it, or re-purpose the article. Hope that helps