USE OF THE DIGITAL OBJECT IDENTIFIER (DOI)
The Digital Object Identifier (DOI) may be used to cite and link to electronic documents.
The DOI consists of a unique alpha-numeric character string which is assigned to a document by the publisher upon the initial electronic publication.
The assigned DOI never changes. Therefore, it is an ideal medium for citing a document, particularly 'Articles in press' because they have not yet received their full bibliographic information.
Example of a correctly given DOI (in URL format; here an article in the journal Annali di Igiene: doi: 10.7416/ai.2015.2033. When you use a DOI to create links to documents on the web, the DOIs are guaranteed never to change.