This is only a sampling of the collections out there, just to get you started!
Books in Primo are assigned Library of Congress Subject Headings. In many ways, subject headings are a form of tagging, in that they represent the content of the material and provide ways for you to efficiently locate more materials that are conceptually related.
Library of Congress Subject Headings are also quite useful for discovering primary sources. The following subheadings usually are added to indicate that the material is a primary source: sources, personal narratives, correspondence, diaries, manuscripts, or notebooks. Once you've discovered the subject heading for secondary sources, try adding one of the primary source subheadings to see what you find. Here are some examples:
Secondary source subject heading: Women -- Europe -- History -- Middle Ages, 500-1500.
Primary source subject heading: Women -- Europe -- History -- Middle Ages, 500-1500 -- Sources.
Secondary source subject heading: United States -- History -- Civil War, 1861-1865.
Primary source subject heading: United States -- History -- Civil War, 1861-1865 -- Personal narratives, Confederate.
Of course, you also can do an author search for your person: