APA Guide 7th ed.

What is a DOI?

DOI stands for Digital Object Identifier.  A DOI is a unique alphanumeric string that is assigned to a source.  Look for the Digital Object Identifier (DOI) when searching for electronic database articles and ebooks.  Be sure to include the DOI at the end of your citation. 

DOI Examples:

• https://doi.org/xxxxx
• https://doi.org/10.18666/TPE-2019-V76-I3-8757
   

DOI Guidelines from APA (p. 298-300):

• Include the DOI when citing print and electronic articles and books (if available)
• Always place the DOI at the end of the citation
• Include a DOI for all works that have a DOI, regardless of whether you used the online or the print version of the work.
• If a print work does not have a DOI, do not include any DOI or URL in the reference list
• Do not add a period after the DOI in the reference list
• If an electronic work has both a DOI and a URL, include only the DOI
• If an online work has a URL but no DOI, include the URL in the reference list

DOI Format (p. 299)

• Present DOIs and URLs as hyperlinks (i.e., beginning with http:// or https://)
• Do not include the words "Retrieved from" or "Accessed from" before a DOI or URL

Why doesn't my source have a DOI?

The DOI system was created in 2000.  Works published before 2000 do not have a DOI unless the publisher retroactively assigned them.  Sometimes even recently published works may not have a DOI either.  Here at JU, most print books do not have a DOI.  An electronic book from a library database (EBSCO, ProQuest, etc.) may or may not have a DOI listed.  APA does not require you to include the URL for electronic articles or books accessed from a database (p. 299).  However, most professors at JU will require you to include the permalink to the source in the database where you retrieved the cited work.  Librarians recommend adding the permalink to the end of the citation.  Learn more about how to create permanent links. (pp. 296, 298-299)