HOW TO:
ThePlagiarismChecker.com queries various popular search engines the phrases and keywords you wish to match. To be most accurate, use two or three phrases. If the majority of your phrases and keywords are found within the same document, there's a good chance this work may have been plagiarized.
If the results show no sign of plagiarism, but you believe otherwise, try using shorter phrases, just a few words long.
An example:
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