APA (7th ed.) Citation

Zipf, G. K. (1972). Human behavior and the principle of least effort : an introduction to human ecology / by G.K. Zipf: An introduction to human ecology. Hafner.

Chicago Style (17th ed.) Citation

Zipf, G. K. Human Behavior and the Principle of Least Effort : An Introduction to Human Ecology / by G.K. Zipf: An Introduction to Human Ecology. Hafner, 1972.

MLA (9th ed.) Citation

Zipf, G. K. Human Behavior and the Principle of Least Effort : An Introduction to Human Ecology / by G.K. Zipf: An Introduction to Human Ecology. Hafner, 1972.

Warning: These citations may not always be 100% accurate.