APA-referens (7:e uppl.)

Butterfiel, W. (1964). Effective personal letters (2nd rev.). Prentice Hall.

Chicago-referens (17:e uppl.)

Butterfiel, W. Effective Personal Letters. 2nd rev. Englewood Cliffs: Prentice Hall, 1964.

MLA-referens (9:e uppl.)

Butterfiel, W. Effective Personal Letters. 2nd rev. Prentice Hall, 1964.