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Unless you know the title and/or author of the book you are looking for, history topics should be searched by Keywordto maximize the number of references to a topic.
Another way to search is to browse by Subject. A subject search is good option if you are trying to narrow down an overly broad topic. For example, World War, 1939-1945 is broken down into 863 subtopics. For the entry World War 1939 1945 Sources, 10 books are listed.
The word "sources" appearing next to an entry is usually a good indication that the text is at least in part a primary source. You can increase your chances of turning up primary sources by adding terms such as "sources," "letters," "diaries," "personal narrative" etc. to your keyword search term.