A DOI or Digital Object Identifier is a unique identification number typically assigned to online articles.

If you are using APA style for your research papers, use the DOI in citations whenever possible. You can usually find the DOI for journal articles in the online database you are using for your research.  If no DOI is present, try the free DOI lookup from CrossRef. For more information, watch the short video, How to find a DOI: And what to do if there is no DOI (Concordia University Library).