Cita APA (7a ed.)

Ward, H. (1978). World powers in the twentieth century. British Broadcasting Corporation.

Cita Chicago Style (17a ed.)

Ward, Harriet. World Powers in the Twentieth Century. London [etc.]: British Broadcasting Corporation, 1978.

Cita MLA (9a ed.)

Ward, Harriet. World Powers in the Twentieth Century. British Broadcasting Corporation, 1978.