The purpose of this is to give some assurance that the information in the article is valid. Trade journals are serials that fall in between the categories of magazines and journals, but their focus includes more product and business information. Primary sources are first hand accounts, original works, or original research, published in either paper or electronic formats. It may be a work of literature or art or an account of an event. Secondary sources are sources that are often based on primary sources, and include reviews, criticism, editorials, and analysis.
Most journal articles are secondary sources which provide analysis, interpretation, or evaluation.
Government publications provide all types of information ranging from broad, general information to focused, contemporary information. The Internet provides access to the full range of information types that is stores in networked computers around the world. Electronic or paper Indexes with abstracts, however, have been carefully prescreened for quality and organized and displayed in ways that make the information easier to use. Bibliographies are lists of citations or references pertaining to a particular subject. The bibliographies are often found at the end of a book or article and contain the sources used there.