Butterfield, W. H. (1951). Effective personal letters (2nd edition.). Prentice-Hall.
Chicago Style aipamenaButterfield, William Henry. Effective Personal Letters. 2nd edition. New York: Prentice-Hall, 1951.
MLA aipamenaButterfield, William Henry. Effective Personal Letters. 2nd edition. Prentice-Hall, 1951.
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