APA (7th ed.) Citation

Ayer, A. J. (1990). The problem of knowledge (Repr., 3. ed.). Penguin Books.

Chicago Style (17th ed.) Citation

Ayer, Alfred J. The Problem of Knowledge. Repr., 3. ed. London: Penguin Books, 1990.

MLA (9th ed.) Citation

Ayer, Alfred J. The Problem of Knowledge. Repr., 3. ed. Penguin Books, 1990.