APA (7th ed.) Citation

Ayer, A. J. (1956). Problem of knowledge. Middlesex Penguin.

Chicago Style (17th ed.) Citation

Ayer, A. J. Problem of Knowledge. Harmondsworth: Middlesex Penguin, 1956.

MLA (9th ed.) Citation

Ayer, A. J. Problem of Knowledge. Middlesex Penguin, 1956.