APA (7th ed.) Citation

Courant, R., & Robbins, H. (1958). What is mathematics? (9. print.). Oxford Univ. Pr.

Chicago Style (17th ed.) Citation

Courant, Richard, and Herbert Robbins. What Is Mathematics? 9. print. London u.a: Oxford Univ. Pr, 1958.

MLA (9th ed.) Citation

Courant, Richard, and Herbert Robbins. What Is Mathematics? 9. print. Oxford Univ. Pr, 1958.

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