APA (7th ed.) Citation

Harris, R. W. (1966). An historical introduction to the twentieth century / by R.W. Harris. Blandford.

Chicago Style (17th ed.) Citation

Harris, R. W. An Historical Introduction to the Twentieth Century / by R.W. Harris. Blandford, 1966.

MLA (9th ed.) Citation

Harris, R. W. An Historical Introduction to the Twentieth Century / by R.W. Harris. Blandford, 1966.

Warning: These citations may not always be 100% accurate.