Cita APA (7a ed.)

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

Cita Chicago Style (17a ed.)

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

Cita MLA (9a ed.)

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