Keene, C. (1959). The Hidden Staircase. Grosset & DunlapPublisher.
Lua i Stíl Chicago (17ú heag.)Keene, Carolyn. The Hidden Staircase. Grosset & DunlapPublisher, 1959.
Lua MLA (8ú heag.)Keene, Carolyn. The Hidden Staircase. Grosset & DunlapPublisher, 1959.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.