Information can generally be assigned to one of the following source types that tend to bear a direct relationship with each other:
These sources are characterized by firsthand (or eyewitness) accounts or are created at the time an event occurred such as transactional receipts or records. These sources lack intermediaries that would otherwise interpret the information. Primary sources are evidence to support research and historical narratives. See SAA Glossary 'primary source'. Some examples are photographs, diaries, letters, raw research data, artifacts (if the object of study).
These sources can be published or unpublished and are removed from one or more primary sources in order to present analyses, interpretations, summaries, derivatives, etc. See ODLIS 'secondary source'. Some examples are journal articles, biographies, film reviews.
These sources generally refer to secondary sources and do not contain original research. As in reference works, these sources are often compiled in order to guide researchers or enthusiasts to information about a topic. See ODLIS, 'tertiary source'. Some examples are encyclopedias, indexes, bibliographies, filmographies.
Source types are not always easy to decipher. They can change according to how they're used or contain elements of multiple source types. Examples include:
- A newspaper article that contains eyewitness interviews (primary) as interpreted by a reporter that was not at the event (secondary).
- Anything can be a primary source if it is the object of research, such as the writings of a historian that are analyzed by a researcher.