Primary sources often reflect the individual perspective, experience, or viewpoint of a participant or observer. A book that was written during the time period you are researching may be considered a primary source. Published letters, personal narratives, diaries, autobiographies, memoirs, and documents are some examples of primary sources that are commonly published in book format.
To find primary sources through Search It, the library catalog, use the "advanced search" feature. Combine your keywords with specific subject terms, such as diaries, correspondence, interviews, etc. Using the subject option will bring back results of everything that a librarian categorized under that heading (so ALL things in the catalog classified as "letters"). If you add a keyword or Any field option, it will search within those subject results for a particular keyword, narrowing your search.
Early English Books Online (EEBO) contains over 22 million digital images of virtually every work printed in the English language as well as works printed in Great Britain and its dependencies from 1473-1700 in any language. Works are drawn from these exhaustive bibliographies and collections of the period: Short-Title Catalogue I (Pollard & Redgrave, 1475 - 1640), Short-Title Catalogue II (Wing, 1641 - 1700), Thomason Tracts, a compendium of broadsides on the English Civil War printed between 1640 and 1661, and Early English Books Tract Supplements.