APA

Easton D., . (1971). The political system. New York: Knopf.

Chicago

Easton David, . 1971. The political system. New York: Knopf.

Harvard

Easton D., . (1971). The political system. New York: Knopf.

MLA

Easton David, . The political system. New York: Knopf. 1971.