Biblio reference display

Hi List.
I am generating documents (article in DB terminology) and thus get some
bibliography to handle.
It works pretty well, except that, when I generate tables, the
bibliographic link gets split like

[
195
]
When the column is too narrow.
This occurs in HTML and FOP output, thus I assume the problem is not
exactly space, as in HTML it should be managed automatically.
How can I force the display to be [195] in a single line ?
I am using this XML for display
...
<entry role="Tab3">
<citation>
	<xref linkend="195" role="bib"/>
</citation>
</entry>
...

Thanks in advance,
Best regards,
Fabien