APA (7th ed.) Citation

O'Brien, G. (1967). An essay on mediæval economic teaching. A. M. Kelley.

Chicago Style (17th ed.) Citation

O'Brien, George. An Essay on Mediæval Economic Teaching. New York: A. M. Kelley, 1967.

MLA (9th ed.) Citation

O'Brien, George. An Essay on Mediæval Economic Teaching. A. M. Kelley, 1967.