Peer-reviewed articles are considered the best examples of research in a given field because of the standards and the long process of review that articles go through to determine the validity and credibility of the research.
Ulrich's Periodical Directory will tell you if a journal is peer-reviewed (refereed). Type in the journal's name and look in the "Refereed" field.
Watch the short tutorial below for more tips on identifying peer-reviewed articles.
The tutorial below demonstrates how to effectively identify a popular source and a scholarly source.