 DOI is like a digital fingerprint for an online document. The purpose of a DOI is to provide a more reliable link to the documents than a URL. It is important to know about DOIs as we use them when referencing journal articles and ebooks in APA style. So how do we find the DOI? You can often find it in the library record. Sometimes it is on the landing page of the journal article or you can try looking on the first page of the article itself. You might find the DOI in different formats. It could look like this or this or this. APA referencing uses the DOI as shown in the first example. Here is how it looks in a reference. So what if there is no DOI? If you have accessed the article via library search, finish the reference after the page numbers. If the article is freely accessible via Google or Google Scholar, use the URL. For more examples, check the CDU APA referencing guide.