Secondary sources provide interpretations and evaluations of primary sources. They are not evidence, but rather commentary on, and discussion of evidence. A newspaper article is a primary source if it reports events, but it is a secondary source if it is an opinion piece which analyses and comments on those events. Secondary sources can simplify the process of finding and evaluating the primary literature e.g. a chemistry textbook.
Examples of secondary sources:
- Biographies
- Documentaries
- Guide books
- Encyclopedias
- History books
- Review articles and literary criticism