Center, S. S., & Persons, G. L. (1941). Teachers' manual and key to workbook, Problems in reading and thinking. The Macmillan Company.
Lua i Stíl Chicago (17ú heag.)Center, Stella S., agus Gladys L. Persons. Teachers' Manual and Key to Workbook, Problems in Reading and Thinking. New York: The Macmillan Company, 1941.
Lua MLA (8ú heag.)Center, Stella S., agus Gladys L. Persons. Teachers' Manual and Key to Workbook, Problems in Reading and Thinking. The Macmillan Company, 1941.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.