Digital Object Identifier (DOI) number is a rapidly expanding naming system used to identify books, documents, music, videos, software and others on the Internet. Because many URLs are unstable and documents are frequently moved within a site or to other sites and databases, DOI makes it easier to find and retrieve documents. DOI numbers are currently assigned for a fee by the DOI Foundation, a non-profit organization. According to CrossRef, the biggest database of DOI numbers, as of April 2011, there are more than 46 million registered DOI numbers. Like the ISBN number used for books, DOI is a unique identifier.

Step 1

Examine the cover page of the printed document to find the DOI number. Publishers who have adopted DOI usually print them at the bottom.

Step 2

Scan the bottom of the Web page to find its DOI number. Keep in mind that a DOI number will only be available for websites that have signed up with the DOI foundation.

Step 3

Go to CrossRef or Bowker and conduct a free DOI lookup search. You can search by author, article title and other publisher information.

Step 4

Remove the hyperlink portion to obtain the DOI number from hyper links. For example, the DOI number of the document with hyper link is simply xx.xxxx/xxxxx.