Comparisons

Hi, Michael Kay  

 I'm working with  two files that compares one another, my principal 
file works with bibliographics references and I'm trying to do a
statisticall by year of kind of used material(books, review, CDs,
etc), part of my file seems like this:

<references>
   <reference>
                <isbn>31316563-xx<isbn>
                <title>ksksk</title>
               <author>Kruscher, John</author>
               <type>book</type>
</reference>


When I do the comparison for type it returns a wrong countings, 
when I use isbn to book and ISSN to reviews it brings me the right countings.

 I've got get the counting for CDs and others , but these don't have a
Standard
Number .

My question  Is there any other way to comparing these elements, a
function,... anything ?


Marcos Hercules