Citazione Stile APA (7a Edizione)

O'Callaghan, B. (2010). A history of the twentieth Century (1. publ., 23. impr.). Longman, part of Pearson.

Citazione stile Chigago Style (17a edizione)

O'Callaghan, Bryn. A History of the Twentieth Century. 1. publ., 23. impr. London [u.a.]: Longman, part of Pearson, 2010.

Citatione MLA (9a ed.)

O'Callaghan, Bryn. A History of the Twentieth Century. 1. publ., 23. impr. Longman, part of Pearson, 2010.