For preliminary assessment of reliability or authenticity, academics frequently distinguish between Primary and Secondary sources of information. Note that this distinction is based on content, and not format.
Primary sources are those that adhere most closely to the original experience or evidence being presented.
In history and the humanities, a primary source is a person, document or account relating direct experience from the time period under study (for example an eyewitness report to an event) or a later recapitulation of events from someone with direct experience (for example an oral history, autobiography or memoir). Historical artifacts such as letters, diaries, interviews, or photographs are all considered primary sources, as are government documents presenting original work, e.g. legislation, hearings, speeches, reports, etc. Creative works such as films, plays, music, poetry and art works can also be considered primary.
In the sciences, a primary source is the original publication of new data, research or theories by the individual(s) producing the data, conducting the research, or formulating the theory. Examples of primary scientific sources include experimental studies, opinion surveys, clinical trials, and data sets. Typically, primary research articles are published in peer-reviewed journal articles with standardized sections, often including a Literature Review, description of Methods, tables of Data, and a summary of Results or formal Conclusion.
Secondary sources are those that summarize, critique or comment on events, data or research presented previously. Since they are one or more steps removed from the event, these sources are considered less reliable in terms of evidence.
Examples of secondary sources include textbooks, review articles, magazine articles, histories, news reports, encyclopedias and other reference books. There can be significant variation in how strictly the terms "primary" and "secondary" are applied by academics, e.g. history professors may consider news articles that were published in the same time period as an historical event to be primary, for purposes of instruction. If in doubt, a student should consult the classroom instructor for guidance.