Research reports in the sciences and social sciences. Especially for recent social history, the best evidence of broad developments in society is often in the form of social science surveys or research studies. This research may be reported in book form, government reports or most commonly in articles published in scholarly journals. Since these are generally very limited in availability and in what they reveal, however, it is also possible to make use of ideas and images conveyed in the mass media, and even in literature, film, popular fiction, self-help literature, textbooks, etc. Again, the point is to use these sources, written or produced at the time, as evidence of how people were thinking.
Secondary sources are works that interpret or analyze an historical event or phenomenon.
They are generally at least one step removed from the event. Encyclopedias and textbooks are also examples of secondary sources. These reference books will give you a good overview of the topic, will outline the basic historical context and will help you identify key participants, dates and publications associated with your topic. Ask a librarian to suggest reference sources, such as specialized encyclopedias, chronologies or factbooks which will give you an historical overview of a topic or event and identify the participants. If you have specific people in mind already, biographical dictionaries and encyclopedias will give you background information and bibliographies of primary and secondary sources.