• Aim for a variety of materials that will provide multiple perspectives on your topic.  In practice, this means using a variety of search strategies and more than one repository or database.
   
• Consult the notes and bibliographies of recently published, good historical monographs and relevant scholarly articles.  If much of the cited primary source material is located in a distant archive, you may need to rethink your approach to your research topic.
   
• Use the author search function in Primo.  You can use "corporate authors" to find writings published by government entities, businesses, or groups.
   
• Look for scholarly editions of primary sources, or for "documentary histories" that include a selection of primary sources accompanied by scholarly annotations.
   
• Use Library of Congress Subject Headings--especially the subheadings most frequently associated with primary sources.

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:

World War, 1939-1945 -- Personal narratives

Saint Petersburg (Russia) -- History -- Siege, 1941-1944 -- Sources

World War, 1939-1945 -- Personal narratives, German

Academic libraries and historical museums often try to digitize primary source collections held in their archives and special collections in order to make them available to the widest possible audience.