Not all analyses of contents are conventionally called "Content Analysis" (CA). Rather, Content Analysis usually only refers to so-called quantitative techniques. These encompass, but are not limited to, frequency counts, concordances, collocation measurements, and a number of clustering techniques for strings and/or codes derived from textual, audial or visual data, sometimes also called "text mining" or "data mining". Content Analysis is also associated with dictionary based analyses of textual data, whereby the distribution of concepts is measured by the distribution of (lemmatized) words in a given text.
Some scholars also speak of "Qualitative Content Analysis" (QCA). In the Fifties, qualitative content analysis merely meant all analytical approaches to textual, audial or video contents, which did not rely on statistical techniques: Contemporary Discourse Analysis, and other more qualitative methods would qualify as "qualitative content analysis" from this point of view. However, today, Qualitative Content Analysis mainly means the interpretive coding of data. The resulting codes can then, of course, be analyzed in quantitative fashion.
Roberts, Carl W. 2001. Content Analysis, in: Neil J. Smelser & Paul B. Baltes (eds.). International Encyclopedia of the Social & Behavioral Sciences. Amsterdam et al.: Elsevier. Concise introduction into the concept of Content Analysis.
Krippendorff, Klaus. 2004. Content Analysis: An Introduction to Its Methodology. 2nd ed. Thousand Oaks, CA: Sage. The currently most frequently used textbook for Content Analysis.
Weber, Robert Philip. 1990. Basic Content Analysis. 2nd ed., Newbury Park, CA: Sage 1990. Short overview of methodologies from the Sage green methods series. Should be read in conjunction with a more comprehensive textbook such as Krippendorff's.
Holsti, Oli R. 1969. Content Analysis for the Social Sciences and Humanities. Reading, MA: Addison-Wesley.
Berelson, Bernard. 1952. Content Analysis in Communication Research. Glencoe, IL: Free Press. The classical formulation of Content Analysis, which paved the road for the quantitative interpretation of content analysis.
Qualitative Content Analysis
Kracauer, Siegfried. 1952. The challenge of qualitative content analysis.
Public Opinion Quarterly 16: 631-642.