Knowls are similar to hyperlinks, except that the target of the
knowl opens within the current web page instead of opening a
new page.  This provides a convenient way to provide supplementary
information, without having to leave the page and then navigate back.

To have knowls on a web page, just put jquery, the knowls script,
and the knowls CSS, in the HTML header.  Adding a knowl is similar
to adding a hyperlink:

<a knowl="target_file">words to click on</a>

Knowls were created by Harald Schilly and made their first appearance
on LMFDB.org in August, 2011.