APA (7th ed.) Citation

ZIPF, G. K. (1972). Human behavior and the Principle of least: Effort; an introduction to human ecology. Hafner publishing Co.

Chicago Style (17th ed.) Citation

ZIPF, George Kingsley. Human Behavior and the Principle of Least: Effort; an Introduction to Human Ecology. New York: Hafner publishing Co, 1972.

MLA (9th ed.) Citation

ZIPF, George Kingsley. Human Behavior and the Principle of Least: Effort; an Introduction to Human Ecology. Hafner publishing Co, 1972.