Different literature types are appropriate for different information needs.
Primary literature reports original findings and new data. In science, research findings are published in peer-reviewed journals. Research papers typically include: Abstract, Introduction, Methods, Results, Discussion, and References. References put the new work in the context of prior work.
New forms of primary literature are increasingly available through digital collections and institutional repositories; these include datasets, laboratory notes, correspondence, diaries, etc.
Examples: Journal of Consulting & Clinical Psychology, Journal of Behavioral Medicine
Secondary literature consists of non-original work: it may be a book or book chapter, review article, summary, interpretation, or critique of primary sources. The best way to find books is by searching the PCOM Catalog and E-ZBorrow, the shared catalog of the PA Academic Libraries Consortium. When searching the PCOM catalog, you have the option of limiting to ebooks or searching both print and electronic collections.
Examples: School Consultation, Mental Health Self-Help
Tertiary literature summarizes, abstracts or indexes the information derived from primary or secondary sources. Encyclopedias, atlases, handbooks, etc. help you to find background information on your topic (such as definitions, names and dates) or take you to relevant books and general articles.
Example: Comprehensive Clinical Psychology, Encyclopedia of Psychology & Religion