Ignoring ampersand(&) as a special character in xml

[Thierry Lam]

Let's say I have the following xml tag:

<para role="source">a & b</para>

Currently, an xml parser will treat & as a special character.  Does
anyone know the special characters to use around the ampersand so that
the xml parser can treat "a & b" as a whole value?

Thanks
Thierry