APA

MacKenzie O., Christensen E. L., Rigby P. H., American Council on Education & National Commission on Accrediting. (1968). Correspondence instruction in the United States: a study of what it is, how it functions, and what its potential may be. New York: McGraw-Hill.

Chicago

MacKenzie Ossian, Christensen Edward L, Rigby Paul H, American Council on Education and National Commission on Accrediting. 1968. Correspondence instruction in the United States: a study of what it is, how it functions, and what its potential may be. New York: McGraw-Hill.

Harvard

MacKenzie O., Christensen E. L., Rigby P. H., American Council on Education and National Commission on Accrediting. (1968). Correspondence instruction in the United States: a study of what it is, how it functions, and what its potential may be. New York: McGraw-Hill.

MLA

MacKenzie Ossian, Christensen Edward L, Rigby Paul H, American Council on Education and National Commission on Accrediting. Correspondence instruction in the United States: a study of what it is, how it functions, and what its potential may be. New York: McGraw-Hill. 1968.