Cita APA (7a ed.)

Sybel, H. v., & Duff Gordon, L. (1861). The history and literature of the Crusades. Chapman and Hall.

Cita Chicago Style (17a ed.)

Sybel, Heinrich von, y Lucie Duff Gordon. The History and Literature of the Crusades. London: Chapman and Hall, 1861.

Cita MLA (8a ed.)

Sybel, Heinrich von, y Lucie Duff Gordon. The History and Literature of the Crusades. Chapman and Hall, 1861.