If you are trying to locate a primary source, books in either print or electronic format can be excellent tools. A primary source is a work that was created at the time of an event by someone present at, or closely related to, the event. Sometimes, primary sources are gathered together and formed into an anthology about a particular historical period. These sources may be modern, book-length editions that contain copies of documents original to the period you are studying.
As you search the Library's WorldCat Discoverycatalog, try using one or two broad keywords describing your topic, and then add the type of document for which you are looking (see suggested terms below). For example, Holocaust AND "personal narrative" or "World War II" AND diary.