Created after the event, often by someone not directly involved.

Used to gain an overview, context, or interpretation of primary sources.

Offer interpretation, analysis, or a summary of primary sources.

Textbooks, articles, reviews, biographies, documentaries, encyclopedias.

Interpretations, analyses, or summaries of primary sources.

Created at the time of the event or shortly thereafter. 

Used to obtain raw data and firsthand evidence. 

Provide direct, unfiltered access to the subject of study 

Diaries, speeches, manuscripts, letters, interviews, original research, artifacts. 

Original, first-hand accounts or direct evidence of an event, object, person, or work of art