How to Evaluate Information Sources: What are tertiary sources?

Tertiary sources of information are based on a collection of primary and secondary sources. Examples of tertiary sources include:

• textbooks (sometimes considered as secondary sources)
• dictionaries and encyclopedias
• manuals, guidebooks, directories, almanacs
• indexes and bibliographies

TIP:  What is considered primary, secondary, or tertiary information may vary according to your field of study. When in doubt, ask your professor.