france and history and sources
"world war" and correspondence
revolution and france and "personal narratives"
Collections of primary sources often have the word documents in the title:
documents and england and reformation
In order to do a subject search, you will need to first identify the appropriate Library of Congress Subject Heading. One way to do this is do a keyword search and then look for relevant items. Note the subject headings assigned to the record and then pair subject headings with the specific subject terms that identify materials as primary sources. For example:
United States--History--Civil War 1861-1865--Pamphlets