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Enter a keyword in the search field under the video below, and it will show up in a heat map, with green meaning "somewhat relevant," and red meaning "very relevant." The results won't only contain the exact keyword you've entered, but also certain related terms. For example, typing "Iraq" will also yield results containing the word "war." I've played with the search engine a bit and I haven't encountered many errors; the rule of thumb seems to be: the longer the word, the better the chance that the search engine will get it right.
Try it out below and tell us what you think in the comments.