Sources that are originally based on the research provided. This includes original written works, poems, diaries, court records, interviews, surveys, original research as well as research published in a scholarly or academic journal.
Sources that are descriptions of other sources. This includes reference material such as encyclopedias, dictionaries, and textbooks. This also includes books, articles, etc., that observe and analyze primary sources.
Sources used to organize and locate secondary sources. This includes Indexes: an alphabetical list of where to locate information typically found at the end of a book.
Located at the beginning of an article that outlines what the article or paper will cover, it summarizes the primary or secondary source.