Pennell, M. E., Cusack, A. M., & Davis, M. (1929). Friends: A primer. Ginn and Company.
Lua i Stíl Chicago (17ú heag.)Pennell, Mary E., Alice M. Cusack, agus Marguerite Davis. Friends: A Primer. Boston ; New York ; Chicago ; London ; Atlanta ; Dallas ; Columbus ; San Francisco: Ginn and Company, 1929.
Lua MLA (8ú heag.)Pennell, Mary E., et al. Friends: A Primer. Ginn and Company, 1929.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.