https://www.catholic.com/encyclopedia/frederick-i
Frederick I | Catholic Answers Encyclopedia
Frederick I, surnamed BARBAROSSA, German King and Roman Emperor, son of Frederick of Swabia (d. 1147) and Judith, daughter of Henry the Black; born c. 1123;...
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https://www.wikidata.org/wiki/Q63770
Frederick I of Saxe-Gotha-Altenburg - Wikidata
First Duke of Saxe-Gotha-Altenburg (1646-1691)
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https://en.wikipedia.org/wiki/Frederick_I_of_Prussia
Frederick I of Prussia - Wikipedia
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https://www.thefamouspeople.com/profiles/frederick-i-holy-roman-emperor-37297.php
Frederick I, Holy Roman Emperor Biography - Facts, Childhood, Family Life & Achievements
Frederick I, Holy Roman Emperor, was Duke of Swabia and the King of Germany in the 12th century.
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https://en.wikipedia.org/wiki/John_Frederick_I,_Elector_of_Saxony
John Frederick I, Elector of Saxony - Wikipedia
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