Saitz, R. L., & Stieglitz, F. B. (1978). Challenge: A first reader/workbook in English. Winthrop Publishers.
Lua i Stíl Chicago (17ú heag.)Saitz, Robert L., agus Francine B. Stieglitz. Challenge: A First Reader/workbook in English. Cambridge, Mass.: Winthrop Publishers, 1978.
Lua MLA (8ú heag.)Saitz, Robert L., agus Francine B. Stieglitz. Challenge: A First Reader/workbook in English. Winthrop Publishers, 1978.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.