Primary sources enable the researcher to get as close as possible to the truth of what actually happened during an event or time period. Primary sources are the evidence left behind by participants or observers. The following are generally considered primary sources:
If you are attempting to find evidence documenting the mentality or psychology of a time, or of a group (evidence of a world view, a set of attitudes, or the popular understanding of an event or condition), the most obvious source is public opinion polls taken at the time. 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.
The most common type of source you are likely to encounter is a secondary source. A secondary source is any source about an event, period, or issue in history that was produced after that event, period or issue has passed.