Duff, A. R. (1969). Pressures. Longman.
Lua i Stíl Chicago (17ú heag.)Duff, Alan R. Pressures. London: Longman, 1969.
Lua MLA (9ú heag.)Duff, Alan R. Pressures. Longman, 1969.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.