A primary source is any record contemporary to an event or time period. Primary sources may be written, oral, visual or physical. Some of these sources were produced with the intent of being preserved for the future. Such intentional sources include government documents, church records, autobiographies or memoirs. On the other hand, many primary sources were produced without any intent of future use. Such unintentional sources may include private correspondence not originally meant for posterity but which later are deposited in archives and libraries. Physical evidence such as buildings, clothing, tools, and landscapes may also be labeled as unintentional sources.
--Galgano, Michael J., J. Christopher Arndt, and Raymond M. Hyser. Doing History: Research and Writing in the Digital Age. Cengage Learning, 2007, p. 57.
Paths Through Historical Sources
Find a good secondary source (book, article), and mine its bibliography. Look for primary sources and types of primary sources used to create the secondary source.
Use sources to find:synonyms/contemporary terms - people's names - place names - event names - military unit names - dates - distinctive quotations and phrases that will lead you to further sources via databases and Google Books.
Use Google Books Advanced search to find key phrases such as names or dates or event names in books written during a certain period and/or with a certain word in the book title, and/or by a certain author