APA

Key V. O., . (1956). American State politics: an introduction. New York: Knopf.

Chicago

Key V O, . 1956. American State politics: an introduction. New York: Knopf.

Harvard

Key V. O., . (1956). American State politics: an introduction. New York: Knopf.

MLA

Key V O, . American State politics: an introduction. New York: Knopf. 1956.