How do I find a DOI number?

A DOI is a persistent Digital Object Identifier, a permanent name used to identify an electronic object. Some other types of persistent location mechanisms include permalinks, PURLs, and stable links. If a DOI exists for your resource, it will be displayed somewhere in the item's record, the full text of the article, the citation, or the abstract. However, not every item will have a DOI. 

If you have located an electronic book or article but were not able to find a DOI, try using the Guest Query Form at Crossref.org. Using the Search Metadata option, complete all the citation information you can, and the result of your search will be the DOI for your article.