Citations: DOI

Many publishers assign a Digital Object Identifiers (DOI) to their digital publications to provide links that are more stable than URLs (more info).

Both APA and MLA styles require the use of DOIs when they are available. In both citation styles the DOI typically falls at the end of the citation.

Don't know the DOI? Try the free DOI Lookup service from Crossref.org.

Crossref provides a number of ways for you to locate a DOI. These links will take you to their website:

• If you have bibliographic data for an item and would like to find the DOI, please use the Metadata Form.
• If you only have an article title and author, use Crossref's Article Title Search
• If you have the text of a bibliographic reference, use Crossref's Simple Text Query
• If you are a developer and wish to submit a raw XML query. use Crossref's XML form