APA (7th ed.) Citation

Opll, F. (1990). Friedrich Barbarossa. Wiss. Buchges.

Chicago Style (17th ed.) Citation

Opll, Ferdinand. Friedrich Barbarossa. Darmstadt: Wiss. Buchges, 1990.

MLA (9th ed.) Citation

Opll, Ferdinand. Friedrich Barbarossa. Wiss. Buchges, 1990.

Warning: These citations may not always be 100% accurate.