APA

Gregory R., . (1971). The origins of American intervention in the First World War. New York: Norton.

Chicago

Gregory Ross, . 1971. The origins of American intervention in the First World War. New York: Norton.

Harvard

Gregory R., . (1971). The origins of American intervention in the First World War. New York: Norton.

MLA

Gregory Ross, . The origins of American intervention in the First World War. New York: Norton. 1971.