Primary sources are materials that provide direct evidence or firsthand testimony concerning the period or subject under investigation. The definition of a primary source may vary depending upon the discipline or context. Examples include:
- Diaries, letters, speeches, interviews, manuscripts
- Memoirs and autobiographies
- Records of organizations and government agencies
- Journal and newspaper articles written at the time
- Photographs, audio recordings, video recordings
- Public opinion polls conducted at the time
- Research reports or articles reflecting the results of scientific experiments or studies
- Works of art, architecture, literature, and music such as paintings, sculptures, musical scores, buildings, novels, poems, etc.
- Artifacts such as plant specimens, fossils, furniture, tools, clothing, etc. of the time under study
Secondary sources interpret or analyze an event or subject. Examples of secondary sources are biographies and journal articles written well after the event or time period under investigation.