Cita APA (7a ed.)

Trager, E. C., & Henderson, S. C. (1956). Pronunciation drills for learners of English. English Language Services.

Cita Chicago Style (17a ed.)

Trager, Edith Crowell, y Sara Cook Henderson. Pronunciation Drills for Learners of English. Washington: English Language Services, 1956.

Cita MLA (9a ed.)

Trager, Edith Crowell, y Sara Cook Henderson. Pronunciation Drills for Learners of English. English Language Services, 1956.