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You may use quotes from unknown sources, proverbs, and those which were published prior to 1923 as long as you cite your source. These are public domain. Short phrases like "Live Life, Love Life" are not eligible for copyright, but may be trademarked (e.g. "Have a Coke and a smile") You can research trademarks here.
"When the power of love overcomes the love of power the world will know peace" is a published lyric by Jimi Hendrix, and would be covered by copyright.
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