"Public opinion and propaganda should be studied in conjunction if one admits that both presuppose specific forms of human behaviour — A general view of the nature of human behaviour will throw light on the psychological mechanisms involved in public opinion and will introduce different techniques of measurement and evaluation — Similarly in the case of propaganda, such knowledge will help to reveal the forms, content, perception and influence of propaganda." (Jean-Marie Van Bol, Abdelfattah Fakhfakh: The use of mass media in the developing countries. Brussels: CIDESA, 1971 Nr. 685, topic code 030)