Berelson, B.Content analysis in communication research, Glencoe, Free Press, 1952.
2.
Kaplan, A. and Goldsen, J.M.Reliability of content analysis categories, in H. D. Lasswell et al. (eds.) Language of politics, New York, Stewart, 1949.
3.
Lasswell, H.D.Describing the contents of communication, in Smith, B. L., Lasswell, H. D., and Casey, R. D. (eds.) Propaganda, communication, and public opinion, Princeton, Princeton University Press, 1946.