APA (7th ed.) Citation

Courant, R., & Robbins, H. (1978). What is mathematics?: An elementary approach to ideas and methods ([4th ed.].). Oxford University Press.

Chicago Style (17th ed.) Citation

Courant, Richard, and Herbert Robbins. What Is Mathematics?: An Elementary Approach to Ideas and Methods. [4th ed.]. Oxford ; New York: Oxford University Press, 1978.

MLA (9th ed.) Citation

Courant, Richard, and Herbert Robbins. What Is Mathematics?: An Elementary Approach to Ideas and Methods. [4th ed.]. Oxford University Press, 1978.