Some assignments will require that you use only "peer reviewed" or "refereed" sources. This means that the writing has been reviewed and vetted by others in the same occupation/research field.
There are several ways to see if a source is peer reviewed: look up the journal in which the article is published using Ulrich's International Periodicals Directory; or, go to the journal's website.
Some databases, including the library's catalogue, will allow you to limit your search results by Scholarly (Peer Reviewed) Journals. Please be advised that this is not a perfect process, and some non-peer reviewed sources may still present themselves. It is up to you to double-check.
Search in Ulrich's to find out whether a journal is peer reviewed.
See our useful tutorials for help crafting a thesis statement, crafting a research topic, identifying key concepts & keywords, finding primary sources, how to cite, and more.