APA (7th ed.) Citation

Keller, J. E. (1967). Alfonso X, el Sabio. Twayne.

Chicago Style (17th ed.) Citation

Keller, John E. Alfonso X, El Sabio. New York: Twayne, 1967.

MLA (9th ed.) Citation

Keller, John E. Alfonso X, El Sabio. Twayne, 1967.