Science literature is made up of primary and secondary literature, or scholarly literature--research reports and analysis--and tertiary literature--news, opinion, and summaries. In most cases, you should use the "most primary" source available for academic work.
Tertiary literature is a general term for non-original or non-scholarly work. Science stories in newspapers are tertiary. Textbooks are also generally considered tertiary, because they report summaries of research and analysis, not original work. Most Dictionaries and Encylopedias are tertiary and should be used for background information, identification of key vocabulary terms for searching, and quick information. See the Background Information Tab above for resources.
Scholarly literature (primary and secondary) is mostly made up of Journal Articles, primarily searched through online databases, or Scholarly Books, searched in the Library Catalog. See the Journal Articles tab and/or the Books tab above for resources.
Websites can be any level of literature. The websites listed in this guide (under the Websites tab) are chosen specifically for quality. Articles and Data sites are mostly Primary or Secondary. General, Educational, and Guides are mostly teritiary.