Butterfiel, W. (1964). Effective personal letters (2nd rev.). Prentice Hall.
Chicago Style (17th ed.) CitationButterfiel, W. Effective Personal Letters. 2nd rev. Englewood Cliffs: Prentice Hall, 1964.
MLA引文Butterfiel, W. Effective Personal Letters. 2nd rev. Prentice Hall, 1964.
警告:這些引文格式不一定是100%准確.