What is a DOI number?
Answer
Many of the articles you'll find in your research have a Digital Object Identifier (DOI) number attached to them, making them easier to get back to for readers checking the citations in a references page. It will often be a string of random-looking numbers; here's one example provided by Business Source Premier, an EBSCO database:
Articles with these numbers assigned to them are unique, so the DOI number referenced will lead only to that article. Generally, DOI numbers, when present, must be included in the citation information you provide about your article.
Attached you'll find rules for citing articles in APA (7th), MLA (8th), and Chicago (17th) formats provided by the Online Writing Lab at Purdue University.