The url element holds the unique resource locator (URL) of an electronic version of the publication or of electronic information relevant to that publication.

## Example

    <pubinfo>
    <pubdate type="primary">
    <date>
    <year>1999</year>
    </date>
    </pubdate>
    <city>Sebastopol</city>
    <publisher>O'Reilly</publisher>
    <serial>1-56592-580-7</serial>
    <address>millera@dinosaurs.upenn.edu</address>
    <url>http://www.dinosaurs.upenn.edu/</url>
    </pubinfo>