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Primary articles are often peer reviewed (sometimes called "refereed"). However, secondary literature, such as review articles may also be peer reviewed.
Peer review means that the article was read and critiqued by other experts on the topic at the request of the editor of the journal. Often the peer reviewers will ask for clarifications or changes to the article. Once the authors have completed their revisions, the article is accepted.You can often determine that an article is peer reviewed by looking at the article for the date received and the date accepted or date published. The article was peer reviewed in the interval between those dates.
Sometimes the indication appears just below the authors and affiliations.
Here's another possibility for indication of peer review near the start of an article:
Sometimes the peer review information is at the bottom of the first page of the article:
Sometimes it is at the end of the article after the references:
Even if you cannot find any dates, the journal could be a peer reviewed journal. Try entering the journal title into Google. The publisher's website for the journal is usually among the first several results. Publishers are proud to publish peer reviewed journals and will usually indicate peer review in their websites. Look for links like "About this Journal," or "Librarian information." Here's an example: