APA (7th ed.) Citation

Lewis, C. S. (1942). The Screwtape letters. Geoffrey Bles, The Centenary Press.

Chicago Style (17th ed.) Citation

Lewis, C. S. The Screwtape Letters. London: Geoffrey Bles, The Centenary Press, 1942.

MLA (9th ed.) Citation

Lewis, C. S. The Screwtape Letters. Geoffrey Bles, The Centenary Press, 1942.