Primary sources can be either published or unpublished, and can be found in many formats, such as manuscripts, books, microfilm, photographs, video and sound recordings. Some primary sources are available in more than one format -- for example, a collection of manuscript letters may also have been published in book form, or may have been digitized and made available on the Internet. Begin by asking two basic questions:
What evidence was created?
For the most part, the evidence used by historians to answer historical questions was not created for that purpose. The evidence of the past -- official records, personal papers, videorecordings, physical remains -- was created to serve the purposes of people with very different agendas. Nonetheless, it is very useful to think about some broad categories of evidence, in part because understanding these categories can help you find the material you need.
What evidence was saved, and where?
Think about who might have collected the material you're hoping to find:
Secondary sources are one step removed from primary sources, though they often quote or otherwise use primary sources. They can cover the same topic, but add a layer of interpretation and analysis. Secondary sources can include: