Books can provide a comprehensive overview of your topic by pointing you towards key ideas, arguments, and thinkers. Scan the index or the table of contents to find the most relevant chapter. Use the bibliography for leads.
Read secondary sources to find primary ones. Skim the notes and references to learn which kinds of evidence scholars adduce in support of their arguments and interpretations. To find items that Coates Library doesn't own, search WorldCat and submit interlibrary loan requests right from the item record.
You can also search for primary sources in WorldCat or the library catalog by using the subject keyword "sources" in an advanced search as pictured below. Look for subject tags such as diaries, letters, memoirs, and accounts to find primary sources.