Main vs additional sources
it offers first-hand testimony of a thought, shows initial information, or papers an event that is historical. These include a study in a log, an image, documentary footage, or a job interview.
A additional supply relays information, providing interpretation and analysis of various other cited source. It's according to main sources. These include publications & articles that discuss information collected off their sources. Encyclopedias autumn in this category, you may hear some individuals reference these as tertiary sources simply because they simply have brief overviews of an interest which are frequently further taken off primary sources compared to typical guide or article.