APA (7th ed.) Citation

Thornton, A. P. (1980). Imperialism in the Twentieth Century. Macmillan Press.

Chicago Style (17th ed.) Citation

Thornton, A. P. Imperialism in the Twentieth Century. London ; Basingstoke: Macmillan Press, 1980.

MLA (8th ed.) Citation

Thornton, A. P. Imperialism in the Twentieth Century. Macmillan Press, 1980.