Primary sources provide first-hand testimony or direct evidence concerning a topic under investigation.
What about Science? In the sciences, a primary source is the published result of experimental or observational research.
Search by keyword for primary sources in Discover
You can search Discover to find direct references to primary source material. Here are some words to include as keywords that would identify a source as primary: correspondence, diaries, early works, interviews, manuscripts, pamphlets, personal narratives, sources, speeches, letters, documents.