Because the pages of your document are in html format, you can reference external resources (images, applets, files, etc.) as usual, in particular you can include html links towards external pages.

If you want furthermore that your reader keep the page of your document while visiting an external page (particularly when your document is in a virtual class), you can use the field ``target'' of the html link.

For example, suppose that you want to reference the site
univ-cotedazur.fr.

Normally, the link looks like

<a href="https://univ-cotedazur.fr/">Nice University</a>

and the result (Nice University (https://univ-cotedazur.fr/)) will lead the reader to quit the document.

But if you write

<a target="wims_external" href="https://univ-cotedazur.fr/">Nice University</a>

the page of Nice University will appear in another window of the browser.

Try it:
Nice University (https://univ-cotedazur.fr/)
