Primary Resources
These are original sources of information on which other research is based, including documents such as poems, diaries, court records, interviews, surveys, and fieldwork. Primary materials also include research results generated by experiments, which are published as journal articles in some fields of study, or as sets of data such as census statistics which have been tabulated but not interpreted.
Secondary Resources
These sources describe or analyze the primary source. Examples of secondary sources include dictionaries, encyclopedias, textbooks, and books and articles that interpret or review research works.
Tertiary Resources
These sources list, compile, digest, or index primary or secondary sources. Examples of tertiary sources include indexes, handbooks, digests, and almanacs.
See the tab titled Cycle of Information for a more detailed description of the differences between these resources.
If you think about the publication details of the information and consider the following you will often find your answer:
Timing of the Event Recorded
If the article was composed close to the time of the event recorded, chances are it is primary material. For instance, a letter written by a soldier during the Vietnam War is primary material, as is an article written in the newspaper or a soldier's letter home during the Civil War. However, an article written analyzing the results of the battle at Gettysburg is secondary material.
Rhetorical Aim of the Written Item
Often, an item that is written with a persuasive or analytical aim is secondary material. Authors of these materials have digested and interpreted the event rather than reported on it.
Context of the Researching Scholar
Primary materials for a critic studying the literature of the Civil War are different from primary materials for a historian studying Civil War prisons. The critic's primary materials are the poems, stories, and films of the era. The research scientist's primary materials would be the diaries and writings of slave families.