APA (7th ed.) Citation

Frost, R., & Untermeyer, L. (1951). The road not taken: An introduction to Robert Frost. Holt.

Chicago Style (17th ed.) Citation

Frost, Robert, and Louis Untermeyer. The Road Not Taken: An Introduction to Robert Frost. New York: Holt, 1951.

MLA (9th ed.) Citation

Frost, Robert, and Louis Untermeyer. The Road Not Taken: An Introduction to Robert Frost. Holt, 1951.