APA

Pfiffner J. P., Davidson R. H., . (1997). Understanding the presidency. New York: Longman.

Chicago

Pfiffner James P, Davidson Roger H, . 1997. Understanding the presidency. New York: Longman.

Harvard

Pfiffner J. P., Davidson R. H., . (1997). Understanding the presidency. New York: Longman.

MLA

Pfiffner James P, Davidson Roger H, . Understanding the presidency. New York: Longman. 1997.