What is a DOI?
A DOI is a Digital Object Identifier, a unique alphanumeric string assigned by the International DOI Foundation to identify content and provide a persistent link to its location on the Internet. The publisher assigns a DOI when the journal article is published and made available electronically.
The DOI is usually located on the first page of the electronic journal article, near the copyright notice. The DOI can also be found on the database landing page for the article.
Other online sources of information like research data may also have DOIs.