Cita APA (7a ed.)

Trager, E., & Henderson, S. (1956). Pronunciation drills for learners of english (1st edition.). English Language Services.

Cita Chicago Style (17a ed.)

Trager, E.C, y S.C Henderson. Pronunciation Drills for Learners of English. 1st edition. Washington, DC: English Language Services, 1956.

Cita MLA (8a ed.)

Trager, E.C, y S.C Henderson. Pronunciation Drills for Learners of English. 1st edition. English Language Services, 1956.