evidence: Muhammad Ali quotes impossible: Impossible is not a fact. It’s an opinion. Impossible is not a declaration. It’s a dare. Impossible is potential. Impossible is temporary. Impossible is nothing." [...] Additional sources for further research "30 Of Muhammad Ali’s Best Quotes." USA Today, Gannett Satellite Information Network, 3 June 2016, www.usatoday.com/story/sports/boxing/2016/06/03/muhammad-ali-best-quotes-boxing/85370850/.