APA (7th ed.) Citation

Ayer, A. J. (1990). The problem of knowledge. Penguin Books.

Chicago Style (17th ed.) Citation

Ayer, Alfred J. The Problem of Knowledge. London: Penguin Books, 1990.

MLA (9th ed.) Citation

Ayer, Alfred J. The Problem of Knowledge. Penguin Books, 1990.

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