In secondary sources, authors analyze and interpret primary source materials. 

Secondary sources can be scholarly or popular.  Scholarly sources (sometimes called "academic" or "peer-reviewed" sources) are written by and for experts and typically include bibliographies and citations.  Popular sources are written for a general, non-expert audience and can be authored by anyone.

PsycINFO is the primary tool used by psychologists to find information related to all aspects of psychology.

Produced by the American Psychological Association (APA) it identifies scholarly journal articles, book chapters, books and dissertations, and is the largest resource devoted to peer-reviewed literature in behavioral science and mental health. Ninety-nine percent of the covered material is peer-reviewed.

Search Biological Sciences and BioOne to find scholarly journal articles and other materials on biomedicine, biotechnology, genetics, neurobiology and other topics related to the biological foundations of neuroscience.