[xsl] ../preceding-sibling/SubDiv1" does not seem to work

["Mark Wilson" <mark@xxxxxxxxxxxx>]

I believe my current context to be inside the second <level2>since value-of 
select="SubDiv1" gives me the contents  of the second SubDiv1.
I now want to know if the two SubDiv1 elements are identical or different. I 
tried ../preceding-sibling/SubDiv1 = SubDiv1, but the first part of the 
expression does not work. What have I misunderstood?
Thanks,
Mark

<Item>
   .....
   <Level2
       <SubDiv1>Voscovec, Jirm. 1905-1981</SubDiv1>
       <SubDiv2>1995. 70th Anniversary Liberated Theater Issue</SubDiv2>
   </Level2>
   <Level2>
       <SubDiv1>Voscovec, Jirm. 1905-1981</SubDiv1>
       <SubDiv2>Personalities of the Liberated Theater Issue</SubDiv2>
     </Level2>
.    ...
</Item>