Butterfiel, W. (1964). Effective personal letters (2nd rev.). Prentice Hall.
Lua i Stíl Chicago (17ú heag.)Butterfiel, W. Effective Personal Letters. 2nd rev. Englewood Cliffs: Prentice Hall, 1964.
Lua MLA (9ú heag.)Butterfiel, W. Effective Personal Letters. 2nd rev. Prentice Hall, 1964.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.