Specifies a jump to a URL (univeral resource location).
The first argument is text to be highlighted (mouseable in HTML browsers) and the second is the URL. In linear documents, the URL is given following the text.
Example:
See also the \urlref{wxWindows manual}
{http://www.aiai.ed.ac.uk/~jacs.html}.
(the line is broken only to keep to this manual's page width).