I need to generate a bookmark for chapter number and head in the same line.

for example in XML.

<p class='chapternumber'>chapter 1</p>
<p class='chapterhead'>chapter title</p>

I did below CSS, but it does not work.

.chapternumber{
string-set: cn contents;
}

.chapterhead{
bookmark-label:string(cn) ": " content(); bookmark-level: 2;
}

kindly help me how can I do.

This example works for me, what is the problem?