1. Aristotle. 1954.The Rhetoric of AristotleEdited by: Roberts, W. Rhys. 1378aNew York
2. Hovland, Carl I., Janis, Irving L. and Kelley, Harold H. 1953.Communication and Persuasion21New Haven
3. Lemert, James B. “Dimensions of Source Credibility.”. Paper read at the 1963 meeting of the Association for Education in Journalism. Omaha.
4. Scales for the measurement of ethos