APA (7th ed.) Citation

Diffie, B. W., & Diffie, J. (1931). Porto Rico: A broken pledge. The Vanguard Press.

Chicago Style (17th ed.) Citation

Diffie, Bailey Wallys, and Justine Diffie. Porto Rico: A Broken Pledge. New York: The Vanguard Press, 1931.

MLA (9th ed.) Citation

Diffie, Bailey Wallys, and Justine Diffie. Porto Rico: A Broken Pledge. The Vanguard Press, 1931.