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Frederick Barbarossa - Wikipedia
Frederick I | Biography, Barbarossa, Crusades, & Facts
Frederick I summary | Britannica
Biography of Frederick I Barbarossa, Holy Roman Emperor
Frederick I (holy Roman Empire) | Encyclopedia.com
Frederick Barbarossa - Wikiwand
Rise of the Red Beard: Who Was Frederick Barbarossa?
Frederick I Barbarossa, Roman Emperor | Encyclopedia.com
Italy - Frederick I, Barbarossa, Empire | Britannica
Frederick I (Frederick Barbarossa) | Encyclopedia.com