Most reference resources are considered "tertiary" source materials. These books and websites provide background information and an overview and analysis of a subject or concept.
Tertiary sources have been compiled from secondary sources. Unlike a secondary source book or journal article, tertiary sources are not intended to be read in their entirety. Instead, they are most often used to clarify terms and concepts about a particular topic. Tertiary sources include:
*Also considered secondary
[Image Source: Idi Amin -Archives New Zealand AAWV 23583]
Subject-specific encyclopedias and dictionaries are more specialized than general ones. Coverage is limited to a specific subject or field of study and contain more developed entries written by scholars and experts within the field.