New Post: Separator between grouped citations

Dear Yves
I have followed your instruction to insert a separator between citations using the following code

<xsl:if test="not(/b:Citation/b:LastAuthor)">

<!-- Comment: place your citation separator here. -->
<xsl:text>;</xsl:text>

</xsl:if>

But it is not working - I have tried for Nature as well as for ACM-Citation Sequence, in both the cases the separator is not being printed.

Here is the output as shown by ACM-Citation Sequence

It has also proved to be effective in protein classification [11] and gene expression-based cancer subtype discovery [12] [13] [5] [14] [1].

And the output by Nature

It has also proved to be effective in protein classification 11 and gene expression-based cancer subtype discovery 12 13 5 14 1.

What I have noticed is that the statement

if test="not(/b:Citation/b:LastAuthor)"

is not getting executed.

Can you help me out please?