In your research, you may find articles from journals or other sources that are not peer-reviewed. For example, working papers are pre-publication versions of journal articles that have NOT gone through the formal peer review process. Working papers can still be appropriate for your paper but if you are not sure, check with your professor.
You may also find journal articles in Google Scholar or other databases that don't allow you to filter for peer review. If you want to check to see if your article is peer-reviewed, you will have to use a special directory of periodicals called Ulrich's. Type in the name of the journal (NOT the article title) and look for the symbol indicating it is peer-reviewed or refereed.
Remember: book reviews, commentary or editorials are typically NOT peer-reviewed even if other articles in the journal are!
Use these databases to supplement your research in EconLit or Google Scholar. Some of these sources can be used to find working papers that may not yet have appeared in journals or that are the final work product.
Use these databases as your main source of articles for your research paper.