DOCBOOK: DocBook: system entities at end of sentence

[Brendan J Simon <Brendan.Simon@ctam.com.au>]

I have a system entity defined for some acronyms.
eg. <!entity gui "<acronym> GUI </acronym>">

How do I use this at the end of a sentence without having a space
between the entity name and the period ?

The following does not work as "gui." is not defined.
<para> X-Windows is a &gui. <para>

The following does work but leaves a space between GUI and the period.
<para> X-Windows is a &gui . <para>

I think that defining another entity with a period at the end is not a
very elegant solution (if it is one at all).
ie. <!entity gui. "<acronym> GUI. </acronym>">

Thanks,
Brendan Simon.