Citazione Stile APA (7a Edizione)

O'Callaghan, B. (1992). A history of the Twentieth Century (1. publ., 6. impression.). Longman.

Citazione stile Chigago Style (17a edizione)

O'Callaghan, Bryn. A History of the Twentieth Century. 1. publ., 6. impression. London [u.a.] New York: Longman, 1992.

Citatione MLA (9a ed.)

O'Callaghan, Bryn. A History of the Twentieth Century. 1. publ., 6. impression. Longman, 1992.