These are contemporary accounts of an event, written by someone who experienced or witnessed the event in question. These original documents (i.e., they are not about another document or account) are often diaries, letters, memoirs, journals, speeches, manuscripts, interviews and other such unpublished works. They may also include published pieces such as newspaper or magazine articles (as long as they are written soon after the fact and not as historical accounts), photographs, audio or video recordings, research reports in the natural or social sciences, or original literary or theatrical works.
The function of these is to interpret primary sources, and so can be described as at least one step removed from the event or phenomenon under review. Secondary source materials, then, interpret, assign value to, conjecture upon, and draw conclusions about the events reported in primary sources. These are usually in the form of published works such as journal articles or books, but may include radio or television documentaries, or conference proceedings.
When evaluating primary or secondary sources, the following questions might be asked to help ascertain the nature and value of material being considered:
Ultimately, all source materials of whatever type must be assessed critically and even the most scrupulous and thorough work is viewed through the eyes of the writer/interpreter. This must be taken into account when one is attempting to arrive at the 'truth' of an event.