The following information has been drawn from the International DOI Foundation (IDF) and APA Style Blog.
A DOI (digital object identifier) is 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 article is published and made available electronically.
DOI numbers start with a 10 followed by a period and contain a prefix and a suffix separated by a slash. The prefix is a unique number of four or more digits assigned to organizations; the suffix is assigned by the publisher and was designed to be flexible with publisher identification standards. The format for DOI in your references: doi:10.xxxx/xxxxx
For more information on the DOI system, consult the Handbook, FAQs and Factsheets from the International DOI foundation.
DOIs are now being recommend in some referencing styles that when DOIs are available you should include them in your citations.
Here is an example of a DOI:
Copyrights and copyfights: copyright law and the digital economy
by Terry Flew; Nicolas Suzor; Bonnie Rui Liu
International Journal of Technology Policy and Law (IJTPL),
Vol. 1, No. 3, 2013
doi: 10.1504/IJTPL.2013.057009
DOIs are usually located on:
Can't find the DOI?
Not all publications have a DOI, and not all databases list DOIs where available.
If you are unable to locate a DOI for a publication, you can use the online free DOI lookup on CrossRef simply enter the author’s surname along with the title of the publication in Search on article title and click "Search".
You can also find a publication by using the DOI resolver on International DOI Foundation. Simply enter the doi and click "Go".
Simple Search Query allows you to copy a whole list of references and returns DOIs for each, if available.
Guest Query provides more options for searching for a DOI.
If you have a DOI and need to find the article information, you can type or paste the DOI into the search box and click Go. Your browser will take you to the publishers web page associated with that DOI.
This tool is drawn from the the web site of the International DOI Foundation.