Keene, C. (1968). Nancy Drew Mystery Stories: Nancy's Mysterious Letter No. 8. Grosset & Dunlap.
Lua i Stíl Chicago (17ú heag.)Keene, Carolyn. Nancy Drew Mystery Stories: Nancy's Mysterious Letter No. 8. New York: Grosset & Dunlap, 1968.
Lua MLA (9ú heag.)Keene, Carolyn. Nancy Drew Mystery Stories: Nancy's Mysterious Letter No. 8. Grosset & Dunlap, 1968.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.